CNPase is a myelin-associated enzyme that makes up 4% of total CNS myelin protein, and is thought to undergo significant age-associated changes.[3] It is named for its ability to catalyze the phosphodiesterhydrolysis of 2',3'-cyclic nucleotides to 2'-nucleotides, though a cohesive understanding of its specific physiologic functions are still ambiguous.[4]
Structural studies have revealed that four classes of CNPases belong to one protein superfamily. CNPase's catalytic core consists of three alpha-helices and nine beta-strands. The proposed mechanism of CNPases phosphodiesterase catalytic activity is similar to the second step of the reaction mechanism for RNase A.[5]
CNPase is expressed exclusively by oligodendrocytes in the CNS, and the appearance of CNPase seems to be one of the earliest events of oligodendrocyte differentiation.[6] CNPase is thought to play a critical role in the events leading up to myelination.[7]
CNPase also associates with microtubules in brain tissue and FRTL-5 thyroid cells, and is reported to have microtubule-associated protein-like activity (MAP; see MAP2), being able to catalyze microtubule formation at low molar ratios. Deletion of the C-terminus of CNPase or phosphorylation abolish the catalytic activity of microtubule formation. CNPase can link tubulin to cellular membranes, and might be involved in the regulation cytoplasmic microtubule distribution.[8]
CNNPase has also been demonstrated to inhibit the replication of HIV-1 and other primate lentiviruses by binding the retroviral Gag protein and inhibiting the genesis of nascent viral particles. Whether this is a biological function of CNPase or a coincidental activity remains unclear.[9]
References
↑Sprinkle TJ, Lanclos KD, Lapp DF (Jul 1992). "Assignment of the human 2',3'-cyclic nucleotide 3'-phosphohydrolase gene to chromosome 17". Genomics. 13 (3): 877–80. doi:10.1016/0888-7543(92)90174-Q. PMID1322358.
↑Sakamoto Y, Tanaka N, Ichimiya T, Kurihara T, Nakamura KT (Feb 2005). "Crystal structure of the catalytic fragment of human brain 2',3'-cyclic-nucleotide 3'-phosphodiesterase". Journal of Molecular Biology. 346 (3): 789–800. doi:10.1016/j.jmb.2004.12.024. PMID15713463.
↑Kasama-Yoshida H, Tohyama Y, Kurihara T, Sakuma M, Kojima H, Tamai Y (Oct 1997). "A comparative study of 2',3'-cyclic-nucleotide 3'-phosphodiesterase in vertebrates: cDNA cloning and amino acid sequences for chicken and bullfrog enzymes". Journal of Neurochemistry. 69 (4): 1335–42. doi:10.1046/j.1471-4159.1997.69041335.x. PMID9326261.
↑Gravel M, Peterson J, Yong VW, Kottis V, Trapp B, Braun PE (Jun 1996). "Overexpression of 2',3'-cyclic nucleotide 3'-phosphodiesterase in transgenic mice alters oligodendrocyte development and produces aberrant myelination". Molecular and Cellular Neurosciences. 7 (6): 453–66. doi:10.1006/mcne.1996.0033. PMID8875429.
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Helfman DM, Shoji M, Kuo JF (Jun 1981). "Purification to homogeneity and general properties of a novel phosphodiesterase hydrolyzing cyclic CMP and cyclic AMP". The Journal of Biological Chemistry. 256 (12): 6327&ndash, 34. PMID6263914.
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