Function
CNPase is a myelin-associated enzyme that makes up 4% of total CNS myelin protein, and is thought to undergo significant age-associated changes. It is named for its ability to catalyze the phosphodiester hydrolysis of 2',3'-cyclic nucleotides to 2'-nucleotides, though a cohesive understanding of its specific physiologic functions are still ambiguous.
Structural studies have revealed that four classes of CNPs belong to one protein superfamily. CNP's catalytic core consists of three alpha-helices and nine beta-strands. The proposed mechanism of CNPs phosphodiesterase catalytic activity is similar to the second step of the reaction mechanism for RNase A.
CNP is expressed exclusively by oligodendrocytes in the CNS, and the appearance of CNP seems to be one of the earliest events of oligodendrocyte differentiation. CNP is thought to play a critical role in the events leading up to myelination.
CNP 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 CNP or phosphorylation abolish the catalytic activity of microtubule formation. CNP can link tubulin to cellular membranes, and might be involved in the regulation cytoplasmic microtubule distribution.
Interestingly, CNP 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 CNP or a coincidental activity remains unclear
Read more about this topic: 2',3'-Cyclic-nucleotide 3'-phosphodiesterase
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