Gamma-butyrobetaine dioxygenase (also known as BBOX, GBBH or γ-butyrobetaine hydroxylase) is an enzyme that in humans is encoded by the BBOX1gene.[1][2] Gamma-butyrobetaine dioxygenase catalyses the formation of L-carnitine from gamma-butyrobetaine, the last step in the L-carnitine biosynthesis pathway.[3]Carnitine is essential for the transport of activated fatty acids across the mitochondrial membrane during mitochondrial beta oxidation.[2] In humans, gamma-butyrobetaine dioxygenase can be found in kidney (high), liver (moderate), and brain (very low).[1][4]BBOX1 has recently been identified as a potential cancergene on the basis of a large-scale microarray data analysis.[5]
This enzyme belongs to the family of oxidoreductases, specifically those acting on paired donors, with O2 as oxidant and incorporation or reduction of oxygen. The oxygen incorporated need not be derived from O2 with 2-oxoglutarate as one donor, and incorporation of one atom of oxygen into each donor. This enzyme participates in lysine degradation. Iron is a cofactor for gamma-butyrobetaine dioxygenase. Similar to many other 2OGoxygenases, the activity of gamma-butyrobetaine dioxygenase can be stimulated by reducing agents such as ascorbate and glutathione.[7][8][9][10] The catalytic activity of gamma-butyrobetaine dioxygenase can be stimulated with different metal ions, especially potassium ions.[11]
Both the apo (PDB id: 3N6W)[12] and the holo (PDB id: 3O2G)[13] structures of gamma-butyrobetaine dioxygenase have been solved, demonstrating an induced fit mechanism may contribute to the catalytic activity of gamma-butyrobetaine dioxygenase.
Gamma-butyrobetaine dioxygenase is promiscus in substrate selectivity and it processes a number of modified substrates, including the natural catalytic products L-carnitine and D-carnitine, forming 3-dehydrocarnitine and trimethylaminoacetone.[13][14] Gamma-butyrobetaine dioxygenase also catalyses the oxidation of mildronate[15] to form multiple products including malonic acid semialdehyde, dimethylamine, formaldehyde and (1-methylimidazolidin-4-yl)acetic acid, which is proposed to be formed via a Stevens rearrangement mechanism.[16][17] Gamma-butyrobetaine dioxygenase is unique among other human 2OGoxygenases that it catalyses both hydroxylation (e.g.: L-carnitine), demethylation (e.g.: formaldehyde) and C-C bond formation (e.g.: (1-methylimidazolidin-4-yl)acetic acid).[18]
Mildronate has a similar structure to the natural substrate gamma-butyrobetaine, with a NH group replacing the CH2 of gamma-butyrobetaine at the C-4 position. A crystal structure of mldronate in complex with gamma-butyrobetaine dioxygenase was published, and it suggests mildronate bind to gamma-butyrobetaine dioxygenase in exactly the same way as gamma-butyrobetaine (PDB id: 3MS5).[32] To date, most enzyme inhibitors for human 2OGoxygenases bind to the cosubstrate 2OG binding site; mildronate is a rare example of a non-peptidyl substrate mimic inhibitor.[33] Although initial reports suggested mildronate is a non-competitive and non-hydroxylatable analogue of gamma-butyrobetaine,[34] further studies have identified mildronate is indeed a substrate for gamma-butyrobetaine dioxygenase.[13][16][35]
Similar to other 2OG oxygenases, gamma-butyrobetaine dioxygenase can be inhibited by 2OG mimics and aromatic inhibitors such as pyridine 2,4-dicarboxylate.[36] Other reported gamma-butyrobetaine dioxygenase inhibitors include cyclopropyl-substituted gamma-butyrobetaines[37] and 3-(2,2-dimethylcyclopropyl)propanoic acid, which is a mechanism-based enzyme inhibitor.[38]
Assay
Several in vitro biochemical assays have been applied to monitor the catalytic activity of gamma-butyrobetaine dioxygenase. Early methods have mainly focused on the use of radiolabeled compounds, including 14C-labelled gamma-butyrobetaine[39] and 14C-labelled 2OG.[40]Enzyme-coupled method have also been applied to detect carnitine formation, by using the enzyme carnitine acetyltransferase and 14C-labelled acetyl-coenzyme A to give labelled acetylcarnitine for detection. Using this method, it is possible to detect carnitine concentration down to the pico-molar range.[41][42][43] Other analytical methods including mass spectrometry and NMR have also been applied,[13] and they are in particularly useful for the study of the coupling ratio between 2OGoxidation and substrate formation, and for the characterisation of unknown enzymatic products.[14] However, these methods are often not suitable for high-throughput screening and require expensiveinstrumentation. A potentially high-throughputfluorescence-based assay has also been proposed by using a fluorinated-gamma-butyrobetaine analog.[44] The fluoride ions released as a result of gamma-butyrobetaine dioxygenase catalyses can be detected by using chemosensors such as protected fluorescein.[45]
↑Paul HS, Sekas G, Adibi SA (Feb 1992). "Carnitine biosynthesis in hepatic peroxisomes. Demonstration of gamma-butyrobetaine hydroxylase activity". European Journal of Biochemistry / FEBS. 203 (3): 599–605. doi:10.1111/j.1432-1033.1992.tb16589.x. PMID1735445.
↑Lindstedt G, Lindstedt S, Nordin I (Oct 1982). "Gamma-butyrobetaine hydroxylase in human kidney". Scandinavian Journal of Clinical and Laboratory Investigation. 42 (6): 477–85. doi:10.3109/00365518209168117. PMID7156861.
↑Dawany NB, Dampier WN, Tozeren A (Jun 2011). "Large-scale integration of microarray data reveals genes and pathways common to multiple cancer types". International Journal of Cancer. 128 (12): 2881–91. doi:10.1002/ijc.25854. PMID21165954.
↑Lindstedt G, Lindstedt S (Aug 1970). "Cofactor requirements of gamma-butyrobetaine hydroxylase from rat liver". The Journal of Biological Chemistry. 245 (16): 4178–86. PMID4396068.
↑Rebouche CJ (Dec 1991). "Ascorbic acid and carnitine biosynthesis". The American Journal of Clinical Nutrition. 54 (6 Suppl): 1147S–1152S. doi:10.1093/ajcn/54.6.1147s. PMID1962562.
↑Nelson PJ, Pruitt RE, Henderson LL, Jenness R, Henderson LM (Jan 1981). "Effect of ascorbic acid deficiency on the in vivo synthesis of carnitine". Biochimica et Biophysica Acta. 672 (1): 123–7. doi:10.1016/0304-4165(81)90286-5. PMID6783120.
↑Furusawa H, Sato Y, Tanaka Y, Inai Y, Amano A, Iwama M, Kondo Y, Handa S, Murata A, Nishikimi M, Goto S, Maruyama N, Takahashi R, Ishigami A (Sep 2008). "Vitamin C is not essential for carnitine biosynthesis in vivo: verification in vitamin C-depleted senescence marker protein-30/gluconolactonase knockout mice". Biological & Pharmaceutical Bulletin. 31 (9): 1673–9. doi:10.1248/bpb.31.1673. PMID18758058.
↑Wehbie RS, Punekar NS, Lardy HA (Mar 1988). "Rat liver gamma-butyrobetaine hydroxylase catalyzed reaction: influence of potassium, substrates, and substrate analogues on hydroxylation and decarboxylation". Biochemistry. 27 (6): 2222–8. doi:10.1021/bi00406a062. PMID3378057.
↑PDB: 3N6W;Tars K, Rumnieks J, Zeltins A, Kazaks A, Kotelovica S, Leonciks A, Sharipo J, Viksna A, Kuka J, Liepinsh E, Dambrova M (Aug 2010). "Crystal structure of human gamma-butyrobetaine hydroxylase". Biochemical and Biophysical Research Communications. 398 (4): 634–9. doi:10.1016/j.bbrc.2010.06.121. PMID20599753.
↑ 13.013.113.213.3PDB: 3O2G; Leung IK, Krojer TJ, Kochan GT, Henry L, von Delft F, Claridge TD, Oppermann U, McDonough MA, Schofield CJ (Dec 2010). "Structural and mechanistic studies on γ-butyrobetaine hydroxylase". Chemistry & Biology. 17 (12): 1316–24. doi:10.1016/j.chembiol.2010.09.016. PMID21168767.
↑Loenarz C, Schofield CJ (Mar 2008). "Expanding chemical biology of 2-oxoglutarate oxygenases". Nature Chemical Biology. 4 (3): 152–6. doi:10.1038/nchembio0308-152. PMID18277970.
↑Sesti C, Simkhovich BZ, Kalvinsh I, Kloner RA (Mar 2006). "Mildronate, a novel fatty acid oxidation inhibitor and antianginal agent, reduces myocardial infarct size without affecting hemodynamics". Journal of Cardiovascular Pharmacology. 47 (3): 493–9. doi:10.1097/01.fjc.0000211732.76668.d2 (inactive 2018-09-22). PMID16633095.
↑Liepinsh E, Vilskersts R, Loca D, Kirjanova O, Pugovichs O, Kalvinsh I, Dambrova M (Dec 2006). "Mildronate, an inhibitor of carnitine biosynthesis, induces an increase in gamma-butyrobetaine contents and cardioprotection in isolated rat heart infarction". Journal of Cardiovascular Pharmacology. 48 (6): 314–9. doi:10.1097/01.fjc.0000250077.07702.23. PMID17204911.
↑Hayashi Y, Kirimoto T, Asaka N, Nakano M, Tajima K, Miyake H, Matsuura N (May 2000). "Beneficial effects of MET-88, a gamma-butyrobetaine hydroxylase inhibitor in rats with heart failure following myocardial infarction". European Journal of Pharmacology. 395 (3): 217–24. doi:10.1016/S0014-2999(00)00098-4. PMID10812052.
↑Pupure J, Isajevs S, Skapare E, Rumaks J, Svirskis S, Svirina D, Kalvinsh I, Klusa V (Feb 2010). "Neuroprotective properties of mildronate, a mitochondria-targeted small molecule". Neuroscience Letters. 470 (2): 100–5. doi:10.1016/j.neulet.2009.12.055. PMID20036318.
↑Liepinsh E, Skapare E, Svalbe B, Makrecka M, Cirule H, Dambrova M (May 2011). "Anti-diabetic effects of mildronate alone or in combination with metformin in obese Zucker rats". European Journal of Pharmacology. 658 (2–3): 277–83. doi:10.1016/j.ejphar.2011.02.019. PMID21371472.
↑Zvejniece L, Svalbe B, Makrecka M, Liepinsh E, Kalvinsh I, Dambrova M (Sep 2010). "Mildronate exerts acute anticonvulsant and antihypnotic effects". Behavioural Pharmacology. 21 (5–6): 548–55. doi:10.1097/FBP.0b013e32833d5a59. PMID20661137.
↑Zhu Y, Zhang G, Zhao J, Li D, Yan X, Liu J, Liu X, Zhao H, Xia J, Zhang X, Li Z, Zhang B, Guo Z, Feng L, Zhang Z, Qu F, Zhao G (Oct 2013). "Efficacy and safety of mildronate for acute ischemic stroke: a randomized, double-blind, active-controlled phase II multicenter trial". Clinical Drug Investigation. 33 (10): 755–60. doi:10.1007/s40261-013-0121-x. PMID23949899.
↑Rose NR, McDonough MA, King ON, Kawamura A, Schofield CJ (Aug 2011). "Inhibition of 2-oxoglutarate dependent oxygenases". Chemical Society Reviews. 40 (8): 4364–97. doi:10.1039/c0cs00203h. PMID21390379.
↑Galland S, Le Borgne F, Guyonnet D, Clouet P, Demarquoy J (Jan 1998). "Purification and characterization of the rat liver gamma-butyrobetaine hydroxylase". Molecular and Cellular Biochemistry. 178 (1–2): 163–8. doi:10.1023/A:1006849713407. PMID9546596.
↑Spaniol M, Brooks H, Auer L, Zimmermann A, Solioz M, Stieger B, Krähenbühl S (Mar 2001). "Development and characterization of an animal model of carnitine deficiency". European Journal of Biochemistry / FEBS. 268 (6): 1876–87. doi:10.1046/j.1432-1327.2001.02065.x. PMID11248709.
↑Ng SF, Hanauske-Abel HM, Englard S (Jan 1991). "Cosubstrate binding site of Pseudomonas sp. AK1 gamma-butyrobetaine hydroxylase. Interactions with structural analogs of alpha-ketoglutarate". The Journal of Biological Chemistry. 266 (3): 1526–33. PMID1988434.
↑Petter RC, Banerjee S, Englard S (1990). "Inhibition of γ-butyrobetaine hydroxylase by cyclopropyl-substituted γ-butyrobetaines". J. Org. Chem. 55 (10): 3088&ndash, 3097. doi:10.1021/jo00297a025.
↑Ziering DL, Pascal Jr RA (1990). "Mechanism-based inhibition of bacterial γ-butyrobetaine hydroxylase". J. Am. Chem. Soc. 112 (2): 834&ndash, 838. doi:10.1021/ja00158a051.
↑Lindstedt G, Lindstedt S, Tofft S (1970). "γ-Butyrobetaine Hydroxylase from Pseudomonas sp AK 1". Biochemistry. 9 (22): 4336&ndash, 4342. doi:10.1021/bi00824a014.
↑Lindstedt G, Lindstedt S, Nordin I (1977). "Purification and properties of γ-butyrobetaine hydroxylase from Pseudomonas species AK 1". Biochemistry. 16 (10): 2181&ndash, 2188. doi:10.1021/bi00629a022.
↑Cederblad C, Lindstedt S (1972). "A method for the determination of carnitine in the picomole range". Clin. Chim. Acta. 37: 235&ndash, 243. doi:10.1016/0009-8981(72)90438-X.
↑Böhmer T, Rydning A, Solberg HE (1974). "Carnitine levels in human serum in health and disease". Clin. Chim. Acta. 57 (1): 55&ndash, 61. doi:10.1016/0009-8981(74)90177-6.
↑Parvin R, Pande SV (1976). "Microdetermination of (−)carnitine and carnitine acetyltransferase activity". Anal. Biochem. 79 (1–2): 190&ndash, 201. doi:10.1016/0003-2697(77)90393-1.
↑Rydzik AM, Leung IK, Kochan GT, Thalhammer A, Oppermann U, Claridge TD, Schofield CJ (Jul 2012). "Development and application of a fluoride-detection-based fluorescence assay for γ-butyrobetaine hydroxylase". Chembiochem. 13 (11): 1559–63. doi:10.1002/cbic.201200256. PMID22730246.
↑Cametti M, Rissanen K (May 2009). "Recognition and sensing of fluoride anion". Chemical Communications (20): 2809–29. doi:10.1039/B902069A. PMID19436879.
Further reading
Olson AL, Rebouche CJ (Jun 1987). "gamma-Butyrobetaine hydroxylase activity is not rate limiting for carnitine biosynthesis in the human infant". The Journal of Nutrition. 117 (6): 1024–31. doi:10.1093/jn/117.6.1024. PMID3110383.
Galland S, Le Borgne F, Bouchard F, Georges B, Clouet P, Grand-Jean F, Demarquoy J (Oct 1999). "Molecular cloning and characterization of the cDNA encoding the rat liver gamma-butyrobetaine hydroxylase". Biochimica et Biophysica Acta. 1441 (1): 85–92. doi:10.1016/s1388-1981(99)00135-3. PMID10526231.
Rigault C, Le Borgne F, Demarquoy J (Dec 2006). "Genomic structure, alternative maturation and tissue expression of the human BBOX1 gene". Biochimica et Biophysica Acta. 1761 (12): 1469–81. doi:10.1016/j.bbalip.2006.09.014. PMID17110165.