Antoniw J F, Cohen P
Eur J Biochem. 1976 Sep;68(1):45-54. doi: 10.1111/j.1432-1033.1976.tb10763.x.
Cyclic-AMP-dependent protein kinase catalyses the activation of phosphorylase kinase and the phosphorylation of two serine residues on the alpha subunit and beta subunit of phosphorylase kinase [Cohen, P., Watson, D.C. and Dixon, G.H. (1975)]. The dephosphorylation of phosphorylase kinase has been shown to be catalysed by two distinct enzymes, termed alpha-phosphorylase kinase phosphatase and beta-phosphorylase kinase phosphatase. These two enzymes show essentially absolute specificity towards the alpha and beta subunits respectively. The two phosphatases copurified through ethanol fractionation, DEAE-cellulose chromatography and ammonium sulphate precipitation, but were separated from each other by a gel filtration on Sephadex G-200. alpha-Phosphorylase kinase phosphatase was purified 500-fold from the ethanol precipitation step, and beta-phosphorylase kinase phosphatase 320-fold. The molecular weights estimated by gel filtration were 170--180 000 for alpha-phosphorylase kinase phosphatase and 75--80 000 for beta-phosphorylase kinase phosphatase. Since the activity of phosphorylase kinase correlates with the state of phosphorylation of the beta subunit (Cohen, P. (1974)), beta-phosphorylase kinase phosphatase is the enzyme which reverses the activation of phosphorylase kinase. alpha-Phosphorylase kinase phosphatase is an enzyme activity that has not been recognised previously. Since the role of the alpha-subunit phosphorylation is to stimulate the rate of dephosphorylation of the beta subunit (Cohen, P. (1974)), alpha-phosphorylase kinase phosphatase can be regarded as the enzyme which inhibits the reversal of the activation of phosphorylase kinase. The implications of these findings for the hormonal control of phosphorylase kinase activity by multisite phosphorylation are discussed.
环磷酸腺苷依赖性蛋白激酶催化磷酸化酶激酶的激活以及磷酸化酶激酶α亚基和β亚基上两个丝氨酸残基的磷酸化[科恩，P.，沃森，D.C.和迪克森，G.H.（1975年）]。已证明磷酸化酶激酶的去磷酸化由两种不同的酶催化，分别称为α-磷酸化酶激酶磷酸酶和β-磷酸化酶激酶磷酸酶。这两种酶分别对α亚基和β亚基表现出基本绝对的特异性。这两种磷酸酶通过乙醇分级分离、二乙氨基乙基纤维素色谱法和硫酸铵沉淀法共同纯化，但通过在葡聚糖凝胶G-200上的凝胶过滤彼此分离。α-磷酸化酶激酶磷酸酶从乙醇沉淀步骤开始纯化了500倍，β-磷酸化酶激酶磷酸酶纯化了320倍。通过凝胶过滤估计的分子量，α-磷酸化酶激酶磷酸酶为170 - 180 000，β-磷酸化酶激酶磷酸酶为75 - 80 000。由于磷酸化酶激酶的活性与β亚基的磷酸化状态相关（科恩，P.（1974年）），β-磷酸化酶激酶磷酸酶是使磷酸化酶激酶激活逆转的酶。α-磷酸化酶激酶磷酸酶是一种以前未被认识的酶活性。由于α亚基磷酸化的作用是刺激β亚基的去磷酸化速率（科恩，P.（1974年）），α-磷酸化酶激酶磷酸酶可被视为抑制磷酸化酶激酶激活逆转的酶。讨论了这些发现对多位点磷酸化对磷酸化酶激酶活性的激素控制的影响。
