Jursinic S B, Robinson J L
Biochim Biophys Acta. 1978 Apr 12;523(2):358-67. doi: 10.1016/0005-2744(78)90038-4.
Rabbit muscle pyruvate kinase has been shown to catalyze the decarboxylation of oxalacetate (Creighton, D.J. and Rose, I.A. (1976) J. Biol. Chem. 251, 61). Noncovalent and covalent modifiers of the enzyme have been used to assess whether the decarboxylase and kinase reactions take place at a common site. Phosphoenol-alpha-ketobutyrate, an analog of the substrate phosphoenol-pyruvate, inhibits decarboxylase and kinase competitively and with nearly identical Ki values (5.7 micron and 4.8 micron, respectively). Oxalate, an analog of enol-pyruvate, inhibits each competitively and with similar Ki values (11 micron and 4.7 micron, respectively). Both activities are lost in parallel upon reaction with dithionitrobenzoate, which is active-site specific. These results indicate that the two activities share a common site on the enzyme. But, effects of the following modifiers suggest that different amino acid residues at that site participate in the two reactions: phenylalanine inhibition and fructose 1,6-bisphosphate activation are more effective with the decarboxylase; iodoacetamide preferentially inactivates decarboxylase while trinitrobenzenesulfonate preferentially inactivates kinase.
已证明兔肌肉丙酮酸激酶可催化草酰乙酸的脱羧反应（Creighton, D.J. 和 Rose, I.A.（1976 年）《生物化学杂志》251 卷，61 页）。该酶的非共价和共价修饰剂已被用于评估脱羧酶反应和激酶反应是否在同一部位发生。磷酸烯醇 -α-酮丁酸是底物磷酸烯醇丙酮酸的类似物，竞争性抑制脱羧酶和激酶，且 Ki 值几乎相同（分别为 5.7 微摩尔和 4.8 微摩尔）。草酸盐是烯醇丙酮酸的类似物，竞争性抑制两者，且 Ki 值相似（分别为 11 微摩尔和 4.7 微摩尔）。与活性位点特异性的二硫代硝基苯甲酸反应后，两种活性会同时丧失。这些结果表明这两种活性在酶上共享一个共同位点。但是，以下修饰剂的作用表明该位点的不同氨基酸残基参与了这两种反应：苯丙氨酸抑制和果糖 1,6 -二磷酸激活对脱羧酶更有效；碘乙酰胺优先使脱羧酶失活，而三硝基苯磺酸优先使激酶失活。
