Duffy T H, Markovitz P J, Chuang D T, Utter M F, Nowak T
Proc Natl Acad Sci U S A. 1981 Nov;78(11):6680-3. doi: 10.1073/pnas.78.11.6680.
Phosphoenolpyruvate carboxykinase [GTP:oxaloacetate carboxy-lyase (transphosphorylating), EC 4.1.1.32] was purified from the liver of several species; the mitochondrial enzyme and the cytosolic enzyme were separated from each other. The species included guinea pig, monkey, rat, and chicken. Each enzyme was assayed for inhibition by the substrate analogues E-2-phosphoenolbutyrate and Z-2-phosphoenolbutyrate. Each enzyme tested displayed the same stereospecificity: the E diastereoisomer was the more potent inhibitor than the Z. These results suggest an active site homology for all carboxykinases. The absolute values for Ki measured show that in almost every case the mitochondrial enzyme is more susceptible to inhibition by these analogues than is the cytosolic enzyme. The Ki values are one-fifth those for the mitochondrial enzymes. These results imply subtle differences in ligand interactions at the active sites of these enzymes.
磷酸烯醇式丙酮酸羧激酶[GTP：草酰乙酸羧基裂解酶（转磷酸化），EC 4.1.1.32]从几种动物的肝脏中纯化得到；线粒体酶和胞质酶彼此分离。这些动物包括豚鼠、猴子、大鼠和鸡。每种酶都用底物类似物E-2-磷酸烯醇丁酸酯和Z-2-磷酸烯醇丁酸酯进行抑制测定。所测试的每种酶都表现出相同的立体特异性：E型非对映异构体是比Z型更有效的抑制剂。这些结果表明所有羧激酶的活性位点具有同源性。所测得的Ki绝对值表明，几乎在每种情况下，线粒体酶比胞质酶更容易受到这些类似物的抑制。线粒体酶的Ki值是胞质酶的五分之一。这些结果意味着这些酶活性位点处配体相互作用存在细微差异。
