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'''2,4 Dienoyl-CoA reductase''' also known as '''DECR1''' is a [[protein]] which in humans is encoded by the ''DECR1'' [[gene]] which resides on [[chromosome 8]].<ref name="entrez">{{cite web | title = Entrez Gene: 2,4-dienoyl CoA reductase 1, mitochondrial| url =https://www.ncbi.nlm.nih.gov/sites/entrez?Db=gene&Cmd=ShowDetailView&TermToSearch=1666 | accessdate = }}</ref><ref name="pmid7818482">{{cite journal |vauthors=Koivuranta KT, Hakkola EH, Hiltunen JK | title = Isolation and characterization of cDNA for human 120 kDa mitochondrial 2,4-dienoyl-coenzyme A reductase | journal = Biochem. J. | volume = 304 | issue = 3| pages = 787–92 |date=December 1994 | pmid = 7818482 | pmc = 1137403 | doi = | url =  }}</ref><ref name="pmid9403065">{{cite journal |vauthors=Helander HM, Koivuranta KT, Horelli-Kuitunen N, Palvimo JJ, Palotie A, Hiltunen JK | title = Molecular cloning and characterization of the human mitochondrial 2,4-dienoyl-CoA reductase gene (DECR) | journal = Genomics | volume = 46 | issue = 1 | pages = 112–9 |date=November 1997 | pmid = 9403065 | doi = 10.1006/geno.1997.5004 | url =  }}</ref>
'''2,4 Dienoyl-CoA reductase''' also known as '''DECR1''' is an [[enzyme]] which in humans is encoded by the ''[[2,4-dienoyl-CoA reductase 1|DECR1]]'' [[gene]] which resides on [[chromosome 8]]. This enzyme catalyzes the following reactions<ref name="entrez">{{cite web | title = Entrez Gene: 2,4-dienoyl CoA reductase 1, mitochondrial| url =https://www.ncbi.nlm.nih.gov/sites/entrez?Db=gene&Cmd=ShowDetailView&TermToSearch=1666 | accessdate = }}</ref><ref name="pmid7818482">{{cite journal |vauthors=Koivuranta KT, Hakkola EH, Hiltunen JK | title = Isolation and characterization of cDNA for human 120 kDa mitochondrial 2,4-dienoyl-coenzyme A reductase | journal = Biochem. J. | volume = 304 | issue = 3| pages = 787–92 |date=December 1994 | pmid = 7818482 | pmc = 1137403}}</ref><ref name="pmid9403065">{{cite journal |vauthors=Helander HM, Koivuranta KT, Horelli-Kuitunen N, Palvimo JJ, Palotie A, Hiltunen JK | title = Molecular cloning and characterization of the human mitochondrial 2,4-dienoyl-CoA reductase gene (DECR) | journal = Genomics | volume = 46 | issue = 1 | pages = 112–9 |date=November 1997 | pmid = 9403065 | doi = 10.1006/geno.1997.5004}}</ref>


This gene encodes an accessory [[enzyme]] that participates in the [[beta oxidation]] and metabolism of polyunsaturated fatty enoyl-CoA esters. Specifically, it catalyzes the reduction of 2,4 Dienoyl-CoA thioesters of varying length by [[NADPH]] cofactor to 3-trans-enoyl-CoA of equivalent length. Unlike the breakdown of saturated fat, [[Cis–trans isomerism|cis]] and [[Cis-trans isomerism|trans]] polyunsaturated fatty acid degradation requires three additional enzymes to generate a product compatible with the standard beta oxidation pathway. DECR is the second such enzyme (The others being [[Enoyl CoA isomerase]] and Dienoyl CoA isomerase) and is the rate limiting step in this auxiliary flow. DECR is capable of reducing both 2-trans,4-cis-dienoyl-CoA and 2-trans,4-trans-dienoyl-CoA thioesters,<ref name="pmid7142199">{{cite journal |vauthors=Cuebas D, Schulz H |title=Evidence for a modified pathway of linoleate degradation. Metabolism of 2,4-decadienoyl coenzyme A |journal=J. Biol. Chem. |volume=257 |issue=23 |pages=14140–4 |date=December 1982 |pmid=7142199 |doi= |url=http://www.jbc.org/cgi/pmidlookup?view=long&pmid=7142199}}</ref> as well as double bonds at odd carbon positions,<ref name="pmid9417087">{{cite journal |vauthors=Filppula SA, Yagi AI, Kilpeläinen SH |title=Delta3,5-delta2,4-dienoyl-CoA isomerase from rat liver. Molecular characterization |journal=J. Biol. Chem. |volume=273 |issue=1 |pages=349–55 |date=January 1998 |pmid=9417087 |doi= 10.1074/jbc.273.1.349|url=http://www.jbc.org/cgi/pmidlookup?view=long&pmid=9417087|display-authors=etal}}</ref> with equal efficiency. At this time, there is no clear explanation for this of lack of stereo-specificity.
[[File:Dienoyl-CoA reductase reaction cis-trans.svg]]
 
DECR1 participates in the [[beta oxidation]] and metabolism of polyunsaturated fatty enoyl-CoA esters. Specifically, it catalyzes the reduction of 2,4 dienoyl-CoA thioesters of varying length by [[NADPH]] cofactor to 3-trans-enoyl-CoA of equivalent length. Unlike the breakdown of saturated fat, [[Cis–trans isomerism|cis]] and [[Cis-trans isomerism|trans]] polyunsaturated fatty acid degradation requires three additional enzymes to generate a product compatible with the standard beta oxidation pathway. DECR is the second such enzyme (the others being [[enoyl CoA isomerase]] and [[dienoyl CoA isomerase]]) and is the rate limiting step in this auxiliary flow. DECR is capable of reducing both 2-trans,4-cis-dienoyl-CoA and 2-trans,4-trans-dienoyl-CoA thioesters<ref name="pmid7142199">{{cite journal |vauthors=Cuebas D, Schulz H |title=Evidence for a modified pathway of linoleate degradation. Metabolism of 2,4-decadienoyl coenzyme A |journal=J. Biol. Chem. |volume=257 |issue=23 |pages=14140–4 |date=December 1982 |pmid=7142199 |doi= |url=http://www.jbc.org/cgi/pmidlookup?view=long&pmid=7142199}}</ref> with equal efficiency.{{Citation needed|date=September 2018}} At this time, there is no clear explanation for this of lack of stereo-specificity.


==Structure==
==Structure==
[[File:2,4 Hexadienoyl-CoA with DECR1.png|thumb|Crystallization<ref name="pmid15531764"/> of DECR with 2,4 Hexadienoyl-CoA and NADPH (not shown). Key residues in the enzyme active site orient the substrate for hydride transfer through a network of hydrogen bonds.]]
Eukaryotic DECR exists in both the [[mitochondria]] (mDECR) and the [[peroxisome]] (pDECR, coded by gene [[DECR2]]). The enzymes from each organelle are [[homology (chemistry)|homologous]] and part of the short-chain dehydrogenase/reductase SDR super-family. mDECR is 124 kDa consisting of 335 amino acids before [[post-translational modification]].<ref name="pmid7818482"/> The secondary structure shares many of the motifs of SDR, including a [[Rossman fold]] for strong NADPH binding. The protein exists as a [[homotetramer]] in physiological environment, but has been shown to also form monomers and dimers in solution.<ref name="pmid15629123">{{cite journal|vauthors=Yu W, Chu X, Chen G, Li D|date=February 2005|title=Studies of human mitochondrial 2,4-dienoyl-CoA reductase|url=http://linkinghub.elsevier.com/retrieve/pii/S0003-9861(04)00612-5|journal=Arch. Biochem. Biophys.|volume=434|issue=1|pages=195–200|doi=10.1016/j.abb.2004.10.018|pmid=15629123}}</ref>


===Gene===
Crystallization of mDECR<ref name="pmid15531764"/> shows the enzyme provides a network of hydrogen bonds from key residues in the active site to NADPH and the 2,4-dienoyl-CoA which positions the hydride at 3.4 Å to the Cδ, compared with 4.0 Å to the Cβ (not shown). The enolate intermediate discussed earlier is stabilized by residues additional hydrogen bonds to Tyr166 and Asn148. Lys214 and Ser210 (conserved residues in all SDR enzymes) are thought to increase the pKa of Tyr166 and stabilize the transition state.<ref name="pmid15531764"/> Additionally, at one end of the active site there is a flexible loop that provides sufficient room for long carbon chains. This likely gives the enzyme flexibility to process fatty acid chains of various lengths. Substrate length for mDECR catalysis is thought to be limited at 20 carbons, at which this very long chain fatty acid is first partially oxidized by pDECR in the peroxisome.<ref name="pmid22745130">{{cite journal |vauthors=Hua T, Wu D, Ding W, Wang J, Shaw N, Liu ZJ |title=Studies of human 2,4-dienoyl CoA reductase shed new light on peroxisomal β-oxidation of unsaturated fatty acids |journal=J. Biol. Chem. |volume=287 |issue=34 |pages=28956–65 |date=August 2012 |pmid=22745130 |doi=10.1074/jbc.M112.385351 |url=http://www.jbc.org/cgi/pmidlookup?view=long&pmid=22745130 |pmc=3436514}}</ref>
The human ''DECR1'' gene has 11 [[exons]] and resides on [[chromosome 8]] at q21.3.<ref name="entrez"/> Sequence alignment indicates that there are five highly conserved acidic [[amino acids|residues]], one of which might act as a [[proton donor]].<ref name="pmid15629123"/>
 
===Protein===
[[File:2,4 Hexadienoyl-CoA with DECR1.png|thumb|Crystallization<ref name="pmid15531764">{{PDB|1w6u}}; {{cite journal |vauthors=Alphey MS, Yu W, Byres E, Li D, Hunter WN | title = Structure and reactivity of human mitochondrial 2,4-dienoyl-CoA reductase: enzyme-ligand interactions in a distinctive short-chain reductase active site | journal = J. Biol. Chem. | volume = 280 | issue = 4 | pages = 3068–77 |date=January 2005 | pmid = 15531764 | doi = 10.1074/jbc.M411069200 | url =  }}</ref> of DECR with 2,4 Hexadienoyl-CoA and NADPH (not shown). Key residues in the enzyme active site orient the substrate for hydride transfer through a network of hydrogen bonds]]
 
Eukaryotic DECR exists in both the [[mitochondria]] (mDECR) and the [[peroxisome]] (pDECR, coded by gene [[DECR2]]). The enzymes from each organelle are [[homology (chemistry)|homologous]] and part of the short-chain dehydrogenase/reductase SDR super-family. mDECR is 124kD consisting of 335 amino acids before [[posttranslational modification]].<ref name="pmid7818482"/> The secondary structure shares many of the motifs of SDR, including a [[Rossman fold]] for strong NADPH binding. The protein exists as a [[homotetramer]] in physiological environment, but has been shown to also form monomers and dimers in solution.<ref name="pmid15629123"/>
 
Crystallization of mDECR<ref name="pmid15531764">{{PDB|1w6u}}; {{cite journal |vauthors=Alphey MS, Yu W, Byres E, Li D, Hunter WN | title = Structure and reactivity of human mitochondrial 2,4-dienoyl-CoA reductase: enzyme-ligand interactions in a distinctive short-chain reductase active site | journal = J. Biol. Chem. | volume = 280 | issue = 4 | pages = 3068–77 |date=January 2005 | pmid = 15531764 | doi = 10.1074/jbc.M411069200 | url =  }}</ref> shows the enzyme provides a network of hydrogen bonds from key residues in the active site to NADPH and the 2,4-dienoyl-CoA which positions the hydride at 3.4 Å to the Cδ, compared with 4.0 Å to the Cβ (not shown). The enolate intermediate discussed earlier is stabilized by residues additional hydrogen bonds to Tyr199 and Asn148. Lys214 and Ser210 (conserved residues in all SDR enzymes) are thought to increase the pKa of Tyr199 and stabilize the transition state.<ref name="pmid15531764">{{PDB|1w6u}}; {{cite journal |vauthors=Alphey MS, Yu W, Byres E, Li D, Hunter WN | title = Structure and reactivity of human mitochondrial 2,4-dienoyl-CoA reductase: enzyme-ligand interactions in a distinctive short-chain reductase active site | journal = J. Biol. Chem. | volume = 280 | issue = 4 | pages = 3068–77 |date=January 2005 | pmid = 15531764 | doi = 10.1074/jbc.M411069200 | url =  }}</ref> Additionally, at one end of the active site there is a flexible loop that provides sufficient room for long carbon chains. This likely gives the enzyme flexibility to process fatty acid chains of various lengths. Substrate length for mDECR catalysis is thought to be limited at 20 carbons, at which the [very long chain fatty acid] is first partially oxidized by pDECR in the peroxisome.<ref name="pmid22745130">{{cite journal |vauthors=Hua T, Wu D, Ding W, Wang J, Shaw N, Liu ZJ |title=Studies of human 2,4-dienoyl CoA reductase shed new light on peroxisomal β-oxidation of unsaturated fatty acids |journal=J. Biol. Chem. |volume=287 |issue=34 |pages=28956–65 |date=August 2012 |pmid=22745130 |doi=10.1074/jbc.M112.385351 |url=http://www.jbc.org/cgi/pmidlookup?view=long&pmid=22745130 |pmc=3436514}}</ref>


==Enzyme Mechanism==
==Enzyme Mechanism==
===Eukaryotic DECR===
===Eukaryotic DECR===
2,4 Dienoyl-CoA thioester reduction by NADPH to 3-Enoyl CoA occurs by a two-step sequential mechanism via an enolate intermediate.<ref name="pmid11591162">{{cite journal |vauthors=Fillgrove KL, Anderson VE |title=The mechanism of dienoyl-CoA reduction by 2,4-dienoyl-CoA reductase is stepwise: observation of a dienolate intermediate |journal=Biochemistry |volume=40 |issue=41 |pages=12412–21 |date=October 2001 |pmid=11591162 |doi= 10.1021/bi0111606|url=https://dx.doi.org/10.1021/bi0111606}}</ref> DECR binds NADPH and the fatty acid thioester and positions them for specific hydride transfer to the Cδ on the hydrocarbon chain. The electrons from the Cγ-Cδ double bond move over to the Cβ-Cγ position, and those from the Cα-Cβ form an enolate. In the final step, a proton is abstracted from the water<ref name="pmid6355075">{{cite journal |vauthors=Mizugaki M, Kimura C, Nishimaki T, Kawaguchi A, Okuda S, Yamanaka H |title=Studies on the metabolism of unsaturated fatty acids. XII. Reaction catalyzed by 2,4-dienoyl-CoA reductase of Escherichia coli |journal=J. Biochem. |volume=94 |issue=2 |pages=409–13 |date=August 1983 |pmid=6355075 |doi= |url=http://jb.oxfordjournals.org/cgi/pmidlookup?view=long&pmid=6355075}}</ref> to the Cα and the thioester is reformed, resulting in a single Cβ-Cγ trans double bond. Since the final proton comes from water, the pH has a significant effect on the catalytic rate with the enzyme demonstrating maximal activity at ~6.0.<ref name="pmid15629123">{{cite journal |vauthors=Yu W, Chu X, Chen G, Li D |title=Studies of human mitochondrial 2,4-dienoyl-CoA reductase |journal=Arch. Biochem. Biophys. |volume=434 |issue=1 |pages=195–200 |date=February 2005 |pmid=15629123 |doi=10.1016/j.abb.2004.10.018 |url=http://linkinghub.elsevier.com/retrieve/pii/S0003-9861(04)00612-5}}</ref> A decrease in activity at pH < 6.0 can be explained by de-protonation of titratable residues that affect protein folding or substrate binding. Mutant proteins with modifications at key acidic [[amino acids]] (E154, E227, E276, D300, D117) show order of magnitude increases in K<sub>m</sub> and/or decreases in V<sub>max</sub>.
2,4 Dienoyl-CoA thioester reduction by NADPH to 3-Enoyl CoA occurs by a two-step sequential mechanism via an enolate intermediate.<ref name="pmid11591162">{{cite journal |vauthors=Fillgrove KL, Anderson VE |title=The mechanism of dienoyl-CoA reduction by 2,4-dienoyl-CoA reductase is stepwise: observation of a dienolate intermediate |journal=Biochemistry |volume=40 |issue=41 |pages=12412–21 |date=October 2001 |pmid=11591162 |doi= 10.1021/bi0111606|url=https://dx.doi.org/10.1021/bi0111606}}</ref> DECR binds NADPH and the fatty acid thioester and positions them for specific hydride transfer to the Cδ on the hydrocarbon chain. The electrons from the Cγ-Cδ double bond move over to the Cβ-Cγ position, and those from the Cα-Cβ form an enolate. In the final step, a proton is abstracted from the water<ref name="pmid6355075">{{cite journal |vauthors=Mizugaki M, Kimura C, Nishimaki T, Kawaguchi A, Okuda S, Yamanaka H |title=Studies on the metabolism of unsaturated fatty acids. XII. Reaction catalyzed by 2,4-dienoyl-CoA reductase of Escherichia coli |journal=J. Biochem. |volume=94 |issue=2 |pages=409–13 |date=August 1983 |pmid=6355075 |doi= |url=http://jb.oxfordjournals.org/cgi/pmidlookup?view=long&pmid=6355075}}</ref> to the Cα and the thioester is reformed, resulting in a single Cβ-Cγ trans double bond. Since the final proton comes from water, the pH has a significant effect on the catalytic rate with the enzyme demonstrating maximal activity at ~6.0. A decrease in activity at pH < 6.0 can be explained by de-protonation of titratable residues that affect protein folding or substrate binding. Mutant proteins with modifications at key acidic [[amino acids]] (E154, E227, E276, D300, D117) show order of magnitude increases in K<sub>m</sub> and/or decreases in V<sub>max</sub>.<ref name="pmid15629123" />
[[File:DECR Mechansim.png|thumb|Proposed mechansim of 2,4-Trans dienoyl-CoA reduction by NADPH in mammalian DECR. The mechanism proceeds stepwise through an enolate intermediate.]]
[[File:DECR Mechansim.png|thumb|Proposed mechanism of 2,4-Trans dienoyl-CoA reduction by NADPH in mammalian DECR. The mechanism proceeds stepwise through an enolate intermediate.]]


===Prokaryotic DECR===
===Prokaryotic DECR===
2,4 Dienoyl-CoA Reductase from [[Escherichia Coli]] (E. Coli) shares very similar kinetic properties to that of eukaryotes, but differs significantly in both structure and mechanism. In addition to NADPH, E. Coli DECR requires a set of [[flavin adenine dinucleotide|FAD]], [[Flavin mononucleotide|FMN]] and [[iron-sulfur cluster]] molecules to complete the electron transfer.<ref name="pmid10933894">{{cite journal |vauthors=Liang X, Thorpe C, Schulz H |title=2,4-Dienoyl-CoA reductase from Escherichia coli is a novel iron-sulfur flavoprotein that functions in fatty acid beta-oxidation |journal=Arch. Biochem. Biophys. |volume=380 |issue=2 |pages=373–9 |date=August 2000 |pmid=10933894 |doi=10.1006/abbi.2000.1941 |url=http://linkinghub.elsevier.com/retrieve/pii/S0003-9861(00)91941-6}}</ref> A further distinction is E. Coli DECR produces the final 2-trans-enoyl-CoA without the need for Enoyl CoA Isomerase.<ref name="pmid6355075"/> The active site contains accurately positioned Tyr199 that donates a proton to the Cγ after hydride attack at the Cδ, completing the reduction in a single concerted step.<ref name="pmid12840019">{{cite journal |vauthors=Hubbard PA, Liang X, Schulz H, Kim JJ |title=The crystal structure and reaction mechanism of Escherichia coli 2,4-dienoyl-CoA reductase |journal=J. Biol. Chem. |volume=278 |issue=39 |pages=37553–60 |date=September 2003 |pmid=12840019 |doi=10.1074/jbc.M304642200 |url=http://www.jbc.org/cgi/pmidlookup?view=long&pmid=12840019}}</ref> Surprisingly, mutation of the Tyr199 does not eliminate enzyme activity but instead changes the product to 3-trans-enoyl-CoA. The current explanation is that Glu164, an acidic residue in the active site, acts as a proton donor to Cα when Tyr199 is not present.<ref name="pmid18171025">{{cite journal |vauthors=Tu X, Hubbard PA, Kim JJ, Schulz H |title=Two distinct proton donors at the active site of Escherichia coli 2,4-dienoyl-CoA reductase are responsible for the formation of different products |journal=Biochemistry |volume=47 |issue=4 |pages=1167–75 |date=January 2008 |pmid=18171025 |doi=10.1021/bi701235t |url=https://dx.doi.org/10.1021/bi701235t}}</ref>
2,4 Dienoyl-CoA Reductase from ''[[Escherichia coli]]'' shares very similar kinetic properties to that of eukaryotes, but differs significantly in both structure and mechanism. In addition to NADPH, E. Coli DECR requires a set of [[flavin adenine dinucleotide|FAD]], [[Flavin mononucleotide|FMN]] and [[iron-sulfur cluster]] molecules to complete the electron transfer.<ref name="pmid10933894">{{cite journal |vauthors=Liang X, Thorpe C, Schulz H |title=2,4-Dienoyl-CoA reductase from Escherichia coli is a novel iron-sulfur flavoprotein that functions in fatty acid beta-oxidation |journal=Arch. Biochem. Biophys. |volume=380 |issue=2 |pages=373–9 |date=August 2000 |pmid=10933894 |doi=10.1006/abbi.2000.1941 |url=http://linkinghub.elsevier.com/retrieve/pii/S0003-9861(00)91941-6}}</ref> A further distinction is E. Coli DECR produces the final 2-trans-enoyl-CoA without the need for Enoyl CoA Isomerase.<ref name="pmid6355075"/> The active site contains accurately positioned Tyr166 that donates a proton to the Cγ after hydride attack at the Cδ, completing the reduction in a single concerted step.<ref name="pmid12840019">{{cite journal |vauthors=Hubbard PA, Liang X, Schulz H, Kim JJ |title=The crystal structure and reaction mechanism of Escherichia coli 2,4-dienoyl-CoA reductase |journal=J. Biol. Chem. |volume=278 |issue=39 |pages=37553–60 |date=September 2003 |pmid=12840019 |doi=10.1074/jbc.M304642200 |url=http://www.jbc.org/cgi/pmidlookup?view=long&pmid=12840019}}</ref> Surprisingly, mutation of the Tyr166 does not eliminate enzyme activity but instead changes the product to 3-trans-enoyl-CoA. The current explanation is that Glu164, an acidic residue in the active site, acts as a proton donor to Cα when Tyr166 is not present.<ref name="pmid18171025">{{cite journal |vauthors=Tu X, Hubbard PA, Kim JJ, Schulz H |title=Two distinct proton donors at the active site of Escherichia coli 2,4-dienoyl-CoA reductase are responsible for the formation of different products |journal=Biochemistry |volume=47 |issue=4 |pages=1167–75 |date=January 2008 |pmid=18171025 |doi=10.1021/bi701235t |url=https://dx.doi.org/10.1021/bi701235t}}</ref>
 
== Function ==


==Function==
DECR is one of three auxiliary enzymes involved in a rate-limiting step of [[unsaturated fat]]ty acid oxidation in mitochondria. In particular, this enzyme contributes to breaking the double bonds at all even-numbered positions, and some double bonds at odd-numbered position.<ref name="pmid15629123"/> The structure of the [[ternary complex]] of pDCR (peroxisomal 2,4-dienoyl CoA reductases) with [[NADP]] and its substrate provides essential and unique insights into the mechanism of [[catalysis]].<ref name="pmid16574148">{{cite journal|last1=Ylianttila|first1=MS|last2=Pursiainen|first2=NV|last3=Haapalainen|first3=AM|last4=Juffer|first4=AH|last5=Poirier|first5=Y|last6=Hiltunen|first6=JK|last7=Glumoff|first7=T|title=Crystal structure of yeast peroxisomal multifunctional enzyme: structural basis for substrate specificity of (3R)-hydroxyacyl-CoA dehydrogenase units.|journal=Journal of Molecular Biology|date=19 May 2006|volume=358|issue=5|pages=1286–95|pmid=16574148|doi=10.1016/j.jmb.2006.03.001}}</ref> Unlike other members belonging to the SDR family, catalysis by pDCR does not involve a [[tyrosine]]-[[serine]] pair.<ref name="pmid15629123"/> Instead, a catalytically critical [[aspartate]], together with an invariant [[lysine]], polarizes a water molecule to donate a [[proton]] for the formation of the product.<ref name="pmid22745130"/> Although pDCR can use 2,4-hexadienoyl CoA as a substrate, the affinities for [[short chain fatty acids]] are lower. Analysis of the hinge movement of DCRs from the [[mitochondrion]] and [[peroxisomes]] sheds light on the reason behind the unique ability of the peroxisome to shorten [[very long chain fatty acids]].<ref name="pmid17847101">{{cite journal|last1=Emekli|first1=U|last2=Schneidman-Duhovny|first2=D|last3=Wolfson|first3=HJ|last4=Nussinov|first4=R|last5=Haliloglu|first5=T|title=HingeProt: automated prediction of hinges in protein structures.|journal=Proteins|date=March 2008|volume=70|issue=4|pages=1219–27|pmid=17847101|doi=10.1002/prot.21613}}</ref>
DECR is one of three auxiliary enzymes involved in a rate-limiting step of [[unsaturated fat]]ty acid oxidation in mitochondria. In particular, this enzyme contributes to breaking the double bonds at all even-numbered positions, and some double bonds at odd-numbered position.<ref name="pmid15629123"/> The structure of the [[ternary complex]] of pDCR (peroxisomal 2,4-dienoyl CoA reductases) with [[NADP]] and its substrate provides essential and unique insights into the mechanism of [[catalysis]].<ref name="pmid16574148">{{cite journal|last1=Ylianttila|first1=MS|last2=Pursiainen|first2=NV|last3=Haapalainen|first3=AM|last4=Juffer|first4=AH|last5=Poirier|first5=Y|last6=Hiltunen|first6=JK|last7=Glumoff|first7=T|title=Crystal structure of yeast peroxisomal multifunctional enzyme: structural basis for substrate specificity of (3R)-hydroxyacyl-CoA dehydrogenase units.|journal=Journal of Molecular Biology|date=19 May 2006|volume=358|issue=5|pages=1286–95|pmid=16574148|doi=10.1016/j.jmb.2006.03.001}}</ref> Unlike other members belonging to the SDR family, catalysis by pDCR does not involve a [[tyrosine]]-[[serine]] pair.<ref name="pmid15629123"/> Instead, a catalytically critical [[aspartate]], together with an invariant [[lysine]], polarizes a water molecule to donate a [[proton]] for the formation of the product.<ref name="pmid22745130"/> Although pDCR can use 2,4-hexadienoyl CoA as a substrate, the affinities for [[short chain fatty acids]] are lower. Analysis of the hinge movement of DCRs from the [[mitochondrion]] and [[peroxisomes]] sheds light on the reason behind the unique ability of the peroxisome to shorten [[very long chain fatty acids]].<ref name="pmid17847101">{{cite journal|last1=Emekli|first1=U|last2=Schneidman-Duhovny|first2=D|last3=Wolfson|first3=HJ|last4=Nussinov|first4=R|last5=Haliloglu|first5=T|title=HingeProt: automated prediction of hinges in protein structures.|journal=Proteins|date=March 2008|volume=70|issue=4|pages=1219–27|pmid=17847101|doi=10.1002/prot.21613}}</ref>


==Clinical Significance==
==Clinical significance==
Mutations in the ''DECR1'' gene may result in [[2,4 Dienoyl-CoA reductase deficiency]],<ref name="pmid2332510">{{cite journal |vauthors=Roe CR, Millington DS, Norwood DL, Kodo N, Sprecher H, Mohammed BS, Nada M, Schulz H, McVie R | title = 2,4-Dienoyl-coenzyme A reductase deficiency: a possible new disorder of fatty acid oxidation | journal = J. Clin. Invest. | volume = 85 | issue = 5 | pages = 1703–7 |date=May 1990 | pmid = 2332510 | pmc = 296625 | doi = 10.1172/JCI114624 | url =  }}</ref> a rare but lethal disorder. More recently, this deficiency has become a common disorder known to result in vomiting, low blood sugar, and even coma.
Mutations in the ''DECR1'' gene may result in [[2,4 Dienoyl-CoA reductase deficiency]],<ref name="pmid2332510">{{cite journal |vauthors=Roe CR, Millington DS, Norwood DL, Kodo N, Sprecher H, Mohammed BS, Nada M, Schulz H, McVie R | title = 2,4-Dienoyl-coenzyme A reductase deficiency: a possible new disorder of fatty acid oxidation | journal = J. Clin. Invest. | volume = 85 | issue = 5 | pages = 1703–7 |date=May 1990 | pmid = 2332510 | pmc = 296625 | doi = 10.1172/JCI114624}}</ref> a rare but lethal disorder.


Due to its role in fatty acid oxidation, DECR may serve as a therapeutic target for treating non-insulin dependent diabetes mellitus ([[NIDDM]]), which features hyperglycemia due to increased fatty acid oxidation.<ref name="pmid15629123"/>
Due to its role in fatty acid oxidation, DECR may serve as a therapeutic target for treating non-insulin dependent diabetes mellitus ([[NIDDM]]), which features hyperglycemia due to increased fatty acid oxidation.<ref name="pmid15629123"/>


In [[Knock-out mice]] studies,<ref name="pmid19578400">{{cite journal |vauthors=Miinalainen IJ, Schmitz W, Huotari A |title=Mitochondrial 2,4-dienoyl-CoA reductase deficiency in mice results in severe hypoglycemia with stress intolerance and unimpaired ketogenesis |journal=PLoS Genet. |volume=5 |issue=7 |pages=e1000543 |date=July 2009 |pmid=19578400 |pmc=2697383 |doi=10.1371/journal.pgen.1000543 |url=http://dx.plos.org/10.1371/journal.pgen.1000543|display-authors=etal}}</ref> DECR1<sup>−/−</sup> subjects accumulate significant concentrations of mono and polyunsaturated fatty acids in the liver during fasting (such as [[oleic acid]], [[palmitoleic acid]], [[linoleic acid]], and [[linolenic acid]]). Mutant subjects were also found to have poor tolerance to cold, decrease in [[diurnal cycle|diurnal]] activity, and an overall reduction in adaptation to metabolic [[stressors]].
In [[Knock-out mice]] studies, DECR1<sup>−/−</sup> subjects accumulate significant concentrations of mono and polyunsaturated fatty acids in the liver during fasting (such as [[oleic acid]], [[palmitoleic acid]], [[linoleic acid]], and [[linolenic acid]]). Mutant subjects were also found to have poor tolerance to cold, decrease in [[diurnal cycle|diurnal]] activity, and an overall reduction in adaptation to metabolic [[stressors]].<ref name="pmid19578400">{{cite journal|display-authors=etal|vauthors=Miinalainen IJ, Schmitz W, Huotari A|date=July 2009|title=Mitochondrial 2,4-dienoyl-CoA reductase deficiency in mice results in severe hypoglycemia with stress intolerance and unimpaired ketogenesis|url=http://dx.plos.org/10.1371/journal.pgen.1000543|journal=PLoS Genet.|volume=5|issue=7|pages=e1000543|doi=10.1371/journal.pgen.1000543|pmc=2697383|pmid=19578400}}</ref>


==See also==
==See also==
* [[Beta oxidation#.CE.B2-oxidation of unsaturated fatty acids]]
*[[Beta oxidation]]
* [[2,4-dienoyl-CoA reductase 1]]
*[[2,4-dienoyl-CoA reductase 1]]


==References==
==References==
 
{{Reflist}}
{{Reflist|2}}


==External links==
==External links==
* {{MeshName|2,4-dienoyl-CoA+reductase}}
*{{MeshName|2,4-dienoyl-CoA+reductase}}


{{Lipid metabolism enzymes}}
{{Lipid metabolism enzymes}}

Latest revision as of 08:34, 10 January 2019

2,4-dienoyl CoA reductase 1, mitochondrial
File:DHFR.png
Crystallographic structure of a tetramer of the ternary complex of DECR1, hexanoyl-coenzyme A, and NADP.[1]
Identifiers
SymbolDECR1
Alt. symbolsDECR
Entrez1666
HUGO2753
OMIM222745
PDB1w6u
RefSeqNM_001359
UniProtQ16698
Other data
EC number1.3.1.34
LocusChr. 8 q21.3

2,4 Dienoyl-CoA reductase also known as DECR1 is an enzyme which in humans is encoded by the DECR1 gene which resides on chromosome 8. This enzyme catalyzes the following reactions[2][3][4]

File:Dienoyl-CoA reductase reaction cis-trans.svg

DECR1 participates in the beta oxidation and metabolism of polyunsaturated fatty enoyl-CoA esters. Specifically, it catalyzes the reduction of 2,4 dienoyl-CoA thioesters of varying length by NADPH cofactor to 3-trans-enoyl-CoA of equivalent length. Unlike the breakdown of saturated fat, cis and trans polyunsaturated fatty acid degradation requires three additional enzymes to generate a product compatible with the standard beta oxidation pathway. DECR is the second such enzyme (the others being enoyl CoA isomerase and dienoyl CoA isomerase) and is the rate limiting step in this auxiliary flow. DECR is capable of reducing both 2-trans,4-cis-dienoyl-CoA and 2-trans,4-trans-dienoyl-CoA thioesters[5] with equal efficiency.[citation needed] At this time, there is no clear explanation for this of lack of stereo-specificity.

Structure

File:2,4 Hexadienoyl-CoA with DECR1.png
Crystallization[1] of DECR with 2,4 Hexadienoyl-CoA and NADPH (not shown). Key residues in the enzyme active site orient the substrate for hydride transfer through a network of hydrogen bonds.

Eukaryotic DECR exists in both the mitochondria (mDECR) and the peroxisome (pDECR, coded by gene DECR2). The enzymes from each organelle are homologous and part of the short-chain dehydrogenase/reductase SDR super-family. mDECR is 124 kDa consisting of 335 amino acids before post-translational modification.[3] The secondary structure shares many of the motifs of SDR, including a Rossman fold for strong NADPH binding. The protein exists as a homotetramer in physiological environment, but has been shown to also form monomers and dimers in solution.[6]

Crystallization of mDECR[1] shows the enzyme provides a network of hydrogen bonds from key residues in the active site to NADPH and the 2,4-dienoyl-CoA which positions the hydride at 3.4 Å to the Cδ, compared with 4.0 Å to the Cβ (not shown). The enolate intermediate discussed earlier is stabilized by residues additional hydrogen bonds to Tyr166 and Asn148. Lys214 and Ser210 (conserved residues in all SDR enzymes) are thought to increase the pKa of Tyr166 and stabilize the transition state.[1] Additionally, at one end of the active site there is a flexible loop that provides sufficient room for long carbon chains. This likely gives the enzyme flexibility to process fatty acid chains of various lengths. Substrate length for mDECR catalysis is thought to be limited at 20 carbons, at which this very long chain fatty acid is first partially oxidized by pDECR in the peroxisome.[7]

Enzyme Mechanism

Eukaryotic DECR

2,4 Dienoyl-CoA thioester reduction by NADPH to 3-Enoyl CoA occurs by a two-step sequential mechanism via an enolate intermediate.[8] DECR binds NADPH and the fatty acid thioester and positions them for specific hydride transfer to the Cδ on the hydrocarbon chain. The electrons from the Cγ-Cδ double bond move over to the Cβ-Cγ position, and those from the Cα-Cβ form an enolate. In the final step, a proton is abstracted from the water[9] to the Cα and the thioester is reformed, resulting in a single Cβ-Cγ trans double bond. Since the final proton comes from water, the pH has a significant effect on the catalytic rate with the enzyme demonstrating maximal activity at ~6.0. A decrease in activity at pH < 6.0 can be explained by de-protonation of titratable residues that affect protein folding or substrate binding. Mutant proteins with modifications at key acidic amino acids (E154, E227, E276, D300, D117) show order of magnitude increases in Km and/or decreases in Vmax.[6]

File:DECR Mechansim.png
Proposed mechanism of 2,4-Trans dienoyl-CoA reduction by NADPH in mammalian DECR. The mechanism proceeds stepwise through an enolate intermediate.

Prokaryotic DECR

2,4 Dienoyl-CoA Reductase from Escherichia coli shares very similar kinetic properties to that of eukaryotes, but differs significantly in both structure and mechanism. In addition to NADPH, E. Coli DECR requires a set of FAD, FMN and iron-sulfur cluster molecules to complete the electron transfer.[10] A further distinction is E. Coli DECR produces the final 2-trans-enoyl-CoA without the need for Enoyl CoA Isomerase.[9] The active site contains accurately positioned Tyr166 that donates a proton to the Cγ after hydride attack at the Cδ, completing the reduction in a single concerted step.[11] Surprisingly, mutation of the Tyr166 does not eliminate enzyme activity but instead changes the product to 3-trans-enoyl-CoA. The current explanation is that Glu164, an acidic residue in the active site, acts as a proton donor to Cα when Tyr166 is not present.[12]

Function

DECR is one of three auxiliary enzymes involved in a rate-limiting step of unsaturated fatty acid oxidation in mitochondria. In particular, this enzyme contributes to breaking the double bonds at all even-numbered positions, and some double bonds at odd-numbered position.[6] The structure of the ternary complex of pDCR (peroxisomal 2,4-dienoyl CoA reductases) with NADP and its substrate provides essential and unique insights into the mechanism of catalysis.[13] Unlike other members belonging to the SDR family, catalysis by pDCR does not involve a tyrosine-serine pair.[6] Instead, a catalytically critical aspartate, together with an invariant lysine, polarizes a water molecule to donate a proton for the formation of the product.[7] Although pDCR can use 2,4-hexadienoyl CoA as a substrate, the affinities for short chain fatty acids are lower. Analysis of the hinge movement of DCRs from the mitochondrion and peroxisomes sheds light on the reason behind the unique ability of the peroxisome to shorten very long chain fatty acids.[14]

Clinical significance

Mutations in the DECR1 gene may result in 2,4 Dienoyl-CoA reductase deficiency,[15] a rare but lethal disorder.

Due to its role in fatty acid oxidation, DECR may serve as a therapeutic target for treating non-insulin dependent diabetes mellitus (NIDDM), which features hyperglycemia due to increased fatty acid oxidation.[6]

In Knock-out mice studies, DECR1−/− subjects accumulate significant concentrations of mono and polyunsaturated fatty acids in the liver during fasting (such as oleic acid, palmitoleic acid, linoleic acid, and linolenic acid). Mutant subjects were also found to have poor tolerance to cold, decrease in diurnal activity, and an overall reduction in adaptation to metabolic stressors.[16]

See also

References

  1. 1.0 1.1 1.2 1.3 PDB: 1w6u​; Alphey MS, Yu W, Byres E, Li D, Hunter WN (January 2005). "Structure and reactivity of human mitochondrial 2,4-dienoyl-CoA reductase: enzyme-ligand interactions in a distinctive short-chain reductase active site". J. Biol. Chem. 280 (4): 3068–77. doi:10.1074/jbc.M411069200. PMID 15531764.
  2. "Entrez Gene: 2,4-dienoyl CoA reductase 1, mitochondrial".
  3. 3.0 3.1 Koivuranta KT, Hakkola EH, Hiltunen JK (December 1994). "Isolation and characterization of cDNA for human 120 kDa mitochondrial 2,4-dienoyl-coenzyme A reductase". Biochem. J. 304 (3): 787–92. PMC 1137403. PMID 7818482.
  4. Helander HM, Koivuranta KT, Horelli-Kuitunen N, Palvimo JJ, Palotie A, Hiltunen JK (November 1997). "Molecular cloning and characterization of the human mitochondrial 2,4-dienoyl-CoA reductase gene (DECR)". Genomics. 46 (1): 112–9. doi:10.1006/geno.1997.5004. PMID 9403065.
  5. Cuebas D, Schulz H (December 1982). "Evidence for a modified pathway of linoleate degradation. Metabolism of 2,4-decadienoyl coenzyme A". J. Biol. Chem. 257 (23): 14140–4. PMID 7142199.
  6. 6.0 6.1 6.2 6.3 6.4 Yu W, Chu X, Chen G, Li D (February 2005). "Studies of human mitochondrial 2,4-dienoyl-CoA reductase". Arch. Biochem. Biophys. 434 (1): 195–200. doi:10.1016/j.abb.2004.10.018. PMID 15629123.
  7. 7.0 7.1 Hua T, Wu D, Ding W, Wang J, Shaw N, Liu ZJ (August 2012). "Studies of human 2,4-dienoyl CoA reductase shed new light on peroxisomal β-oxidation of unsaturated fatty acids". J. Biol. Chem. 287 (34): 28956–65. doi:10.1074/jbc.M112.385351. PMC 3436514. PMID 22745130.
  8. Fillgrove KL, Anderson VE (October 2001). "The mechanism of dienoyl-CoA reduction by 2,4-dienoyl-CoA reductase is stepwise: observation of a dienolate intermediate". Biochemistry. 40 (41): 12412–21. doi:10.1021/bi0111606. PMID 11591162.
  9. 9.0 9.1 Mizugaki M, Kimura C, Nishimaki T, Kawaguchi A, Okuda S, Yamanaka H (August 1983). "Studies on the metabolism of unsaturated fatty acids. XII. Reaction catalyzed by 2,4-dienoyl-CoA reductase of Escherichia coli". J. Biochem. 94 (2): 409–13. PMID 6355075.
  10. Liang X, Thorpe C, Schulz H (August 2000). "2,4-Dienoyl-CoA reductase from Escherichia coli is a novel iron-sulfur flavoprotein that functions in fatty acid beta-oxidation". Arch. Biochem. Biophys. 380 (2): 373–9. doi:10.1006/abbi.2000.1941. PMID 10933894.
  11. Hubbard PA, Liang X, Schulz H, Kim JJ (September 2003). "The crystal structure and reaction mechanism of Escherichia coli 2,4-dienoyl-CoA reductase". J. Biol. Chem. 278 (39): 37553–60. doi:10.1074/jbc.M304642200. PMID 12840019.
  12. Tu X, Hubbard PA, Kim JJ, Schulz H (January 2008). "Two distinct proton donors at the active site of Escherichia coli 2,4-dienoyl-CoA reductase are responsible for the formation of different products". Biochemistry. 47 (4): 1167–75. doi:10.1021/bi701235t. PMID 18171025.
  13. Ylianttila, MS; Pursiainen, NV; Haapalainen, AM; Juffer, AH; Poirier, Y; Hiltunen, JK; Glumoff, T (19 May 2006). "Crystal structure of yeast peroxisomal multifunctional enzyme: structural basis for substrate specificity of (3R)-hydroxyacyl-CoA dehydrogenase units". Journal of Molecular Biology. 358 (5): 1286–95. doi:10.1016/j.jmb.2006.03.001. PMID 16574148.
  14. Emekli, U; Schneidman-Duhovny, D; Wolfson, HJ; Nussinov, R; Haliloglu, T (March 2008). "HingeProt: automated prediction of hinges in protein structures". Proteins. 70 (4): 1219–27. doi:10.1002/prot.21613. PMID 17847101.
  15. Roe CR, Millington DS, Norwood DL, Kodo N, Sprecher H, Mohammed BS, Nada M, Schulz H, McVie R (May 1990). "2,4-Dienoyl-coenzyme A reductase deficiency: a possible new disorder of fatty acid oxidation". J. Clin. Invest. 85 (5): 1703–7. doi:10.1172/JCI114624. PMC 296625. PMID 2332510.
  16. Miinalainen IJ, Schmitz W, Huotari A, et al. (July 2009). "Mitochondrial 2,4-dienoyl-CoA reductase deficiency in mice results in severe hypoglycemia with stress intolerance and unimpaired ketogenesis". PLoS Genet. 5 (7): e1000543. doi:10.1371/journal.pgen.1000543. PMC 2697383. PMID 19578400.

External links