The mechanism and control of protein degradation in cells are quite mysterious. We investigated the change of protease activities in animals fed a vitamin E-deficient diet. The Ca2+-activated protease activity was not significantly changed in vitamin E-deficient rats during the 45 weeks of the experiment. The cathepsin B activity was increased in those animals. Electron microscopic observation on the muscle of the vitamin E-deficient rats showeddestruction of myofibrils at the Z-line, narrowness of myofibrils, and dispersed myofibrils. The M-line, which is known to disappear with cathepsin L treatment, was clearly observed. The phagocytosis of muscle cells by macrophages was also observed. These results show that the abnormal myofibril protein degradation in muscle tissue of vitamin E-deficient rats is not only due to the activation of macrophages and the increment oflysosomes in muscle cells, but also due to the protease which can destroy the myofibril at the Z-line. It may be a Ca2+-activated protease.
A low calcium requiring form of calcium activated protease (LCAP)and a high calcium requiring form of calcium activated protease (HCAP), purified from porcine skeletal muscle, were studied. LCAPwas most active at pH 8.2. The HCAPwas rather unstable at high temperature or at alkaline pHs: The antiserum to purified LCAPdid not make a precipitin line with HCAP.Those proteases hydrolyzed myofibril proteins to disassemble the structure of myofibrils. The electronmicrogram of the myofibril treated by LCAPresembled that of the muscle obtained from a vitamin E deficient rat. Both LCAP and HCAPhydrolyzed purified a-actinin, liver actin, and some other proteins which are not assigned. The microsomeproteins were resistant to protease treatment, and only the 180kd protein was hydrolyzed by LCAP.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.