Shur S A, Vulfson P L, Severin S E
Biochem Int. 1983 Aug;7(2):197-206.
In native nonactivated phosphorylase kinase [14C] iodacetamide interacts with 50 cysteinyl residues per enzyme molecule (alpha beta gamma delta)4. According to their reactivity towards iodacetamide these residues can be classified into 3 groups. The most reactive cysteinyl residues are involved in the enzyme activation caused by modification of SH-groups. The enzyme inhibition is biphasic. The fast and slow inactivation reactions follow the pseudo-first order kinetics. The rate of inactivation is increased by Ca2+. Mg-ATP effectively protects the enzyme against the inactivation and chemical modification of three SH-groups per protomer (apha beta gamma delta). The kinetics of inactivation and of the [14C] iodacetamide label incorporation demonstrate that two cysteinyl residues per enzyme protomer (alpha beta gamma delta) are essential for the enzyme activity. These residues are located near the ATP-binding site of the beta and gamma subunits of phosphorylase kinase.
在天然未活化的磷酸化酶激酶中，[14C]碘乙酰胺与每个酶分子（αβγδ）4中的50个半胱氨酰残基相互作用。根据它们对碘乙酰胺的反应性，这些残基可分为3组。反应性最强的半胱氨酰残基参与由巯基修饰引起的酶激活。酶抑制是双相的。快速和缓慢失活反应遵循准一级动力学。Ca2+可提高失活速率。Mg-ATP可有效保护酶免予失活以及每个原体（αβγδ）中三个巯基的化学修饰。失活动力学和[14C]碘乙酰胺标记掺入表明，每个酶原体（αβγδ）中的两个半胱氨酰残基对酶活性至关重要。这些残基位于磷酸化酶激酶β和γ亚基的ATP结合位点附近。
