Waelkens E, Goris J, Merlevede W
FEBS Lett. 1985 Nov 18;192(2):317-20. doi: 10.1016/0014-5793(85)80133-2.
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.
兔骨骼肌中一种新发现的250 kDa聚阳离子刺激（PCSM）蛋白磷酸酶的抑制剂-1磷酸酶活性，而非磷酸化酶磷酸酶活性，可被一种Ca2+依赖性蛋白酶提高至10倍。在该酶的纯化过程中，PCSH和PCSL磷酸酶不敏感的酶定向蛋白酶效应逐渐丧失。这可以通过酶缓慢转化为具有特异性改变的活性形式，或者丧失抑制剂-1磷酸酶活性的蛋白酶敏感抑制剂来解释，从而产生一种以高抑制剂-1/磷酸化酶α活性比为特征的PC磷酸酶。EGTA或亮抑蛋白酶肽可完全抑制Ca2+依赖性蛋白酶。
