Calpain and calpastatin in pig retina
Yoshimura, N.; Tsukahara, I.; Murachi, T.
Nippon Ganka Gakkai Zasshi 89(9): 1034-1038
1985
ISSN/ISBN: 0029-0203 PMID: 3002158 Document Number: 245926
In pig retina, we found two forms of Ca-dependent cysteine proteinase (Calpain, EC 3. 4. 22. 17) and their specific endogenous inhibitor protein (Calpastatin). Calpain I (low Ca-requring form) was half-maximally activated at 8 .mu.M calcium, and calpain II (high Ca-requiring from) at 250 .mu.M calcium. Both calpain I and calpain II were inhibited by calpastatin and calpastatin was specific to calpain. By using an immunoblotting method, calpain I and calpain II from pig retina were indistinguishable from calpains I and II of other organs of pig. Microtubule-associated proteins 1 and 2 were shown to be very susceptible to the proteolysis by either calpain I or calpain II.