title: Activation of the PCSM-protein phosphatase by a Ca2+-dependent protease.
abstract: The inhibitor-1 phosphatase but not the phosphorylase phosphatase activity of a newly discovered 250 kDa polycation-stimulated (PCSM) protein phosphatase in rabbit skeletal muscle is increased up to 10-fold by a Ca2+-dependent protease. The enzyme-directed protease effect to which the PCSH and PCSL phosphatases are insensitive was progressively lost during purification of the enzyme. This could be explained by either a slow conversion of the enzyme to an active form of the enzyme with a change in specificity, or the loss of a protease-sensitive inhibitor of the inhibitor-1 phosphatase activity, resulting in a PCS phosphatase characterized by its high inhibitor-1/phosphorylase alpha activity ratio. The Ca2+-dependent protease is completely inhibited by EGTA or leupeptin.
mesh_terms: D000818:Animals; D002154:Calpain / Q000378:metabolism*; D004533:Egtazic Acid / Q000494:pharmacology; D004789:Enzyme Activation; D007700:Kinetics; D007976:Leupeptins / Q000494:pharmacology; D009132:Muscles / Q000201:enzymology*; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D011817:Rabbits
chemical_list: D007976:Leupeptins; D004533:Egtazic Acid; D010749:Phosphoprotein Phosphatases; D002154:Calpain; C032854:leupeptin