The susceptibility of glycogen phosphorylase to inactivation by endogenous and exogenous proteases.

摘要: Phosphorylases a and b were inactivated very rapidly by neutral, trypsin-like protease from rat intestinal muscle. With 32P-phosphorylase as substrate, it was shown that the initial event in inactivation release of small, phosphopeptide N-terminus enzyme, leaving original 100,000 subunit form virtually unchanged. Subsequent proteolysis limited, producing 85, 70 65,000 mol. wt. derivatives. The effects several allosteric modulators phosphorylase on rates two enzymes studied. Removal pyridoxal phosphate cofactor increased susceptibility three fold while unaffected. By comparison these with those obtained digestion trypsin chymotrypsin, is concluded muscle has markedly enhanced ability for inactivating their native conformation. Assuming this property reflected vivo, possible role such neutral proteases initiating protein degradation advanced.