Calcium-dependent neutral proteases

Kishimoto, A., Mikawa, K., Hashimoto, K., Yasuda, I., Tanaka, S., Tominaga, M., Kuroda, T., and Nishizuka, Y. (1989). Limited proteolysis of protein kinase C subspecies by calcium-dependent neutral protease (calpain). J Biol Chem 264, 4088-4092. 

Activation of Calpain (Calcium-Dependent Neutral Protease).147... 

Takai, Y., Yamamoto, M., Inoue, M., Kishimoto, A., and Nishizuka, Y., 1977, A proenzyme of cyclic nucleotide-independent protein kinase and its activation by calcium-dependent neutral protease from rat liver, Biochem. Biophys. Res. Commun. 77 542. 

The Ca2+-dependent neutral proteases called calpains are found within the cells of higher animals. The 705-residue multidomain peptide chain of a chicken calpain contains a papain-like domain as well as a calmodulin-like domain.328 It presumably arose from fusion of the genes of these proteins. At least six calpains with similar properties are known.329 Some have a preference for myofibrillar proteins or neurofilaments.330 They presumably function in normal turnover of these proteins and may play a role in numerous calcium-activated cellular processes.331-3323... 

A few enzymes, such as the previously mentioned CNP, are believed to be fairly specific for myelin/oligodendro-cytes. There is much more in the CNS than in peripheral nerve, suggesting some function more specialized to the CNS. In addition, a unique pH 7.2 cholesterol ester hydrolase is also enriched in myelin. On the other hand, there are many enzymes that are not myelin-specific but appear to be intrinsic to myelin and not contaminants. These include cAMP-stimulated kinase, calcium/calmodulin-dependent kinase, protein kinase C, a neutral protease activity and phosphoprotein phosphatases. The protein kinase C and phosphatase activities are presumed to be responsible for the rapid turnover of MBP phosphate groups, and the PLP acylation enzyme activity is also intrinsic to myelin. 

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