Biological Station, Gdansk University, 80-680, Gdansk-Sobieszewo, Poland.
Fish Physiol Biochem. 1988 Oct;5(4):241-8. doi: 10.1007/BF01874801.
Mitochondrial NAD(P)-dependent malic enzyme [EC 1.1.1.39, L-malate: NAD(+) oxidoreductase (decarboxylating)] was purified from herring skeletal muscle to a specific activity of 8.2 μmol/min/mg. The purification procedure involved chromatography on DEAE-cellulose, Red Agarose and a Sephacryl S-300 with a final recovery of 38% of enzyme activity. This enzyme catalyzes the oxidative decarboxylation of malate in the presence of either NAD or NADP in the presence of Mn(2+). Some kinetic characteristics of this enzyme were determined. The pH optimum of activity is 7.0. ATP was shown to be a competitive inhibitor with malate. The inhibition by ATP displayed hyperbolic competitive kinetics with a Ki (ATP) of 0.28 mM in the presence of NAD and 0.75 mM in the presence of NADP. Fumarate reversed ATP inhibition.In vivo, regulation of NAD(P)-dependent malic enzyme might respond to changing levels of mitochondrial ATP and fumarate with the enzyme undergoing kinetic activation by an increase in the concentration of mitochondrial fumarate which could reverse enzyme inhibition by ATP.
来自鲱鱼骨骼肌的线粒体 NAD(P)-依赖性苹果酸酶 [EC 1.1.1.39，L-苹果酸：NAD(+)氧化还原酶（脱羧）] 被纯化到 8.2 μmol/min/mg 的比活。纯化程序包括 DEAE-纤维素、红琼脂糖和 Sephacryl S-300 的层析，最终酶活性回收率为 38%。该酶在 Mn(2+)存在下，催化苹果酸在 NAD 或 NADP 存在下的氧化脱羧。该酶的一些动力学特性已被确定。活性的 pH 最适值为 7.0。ATP 被证明是苹果酸的竞争性抑制剂。在 NAD 存在时，ATP 的抑制作用呈双曲线竞争性动力学，Ki (ATP) 为 0.28 mM，在 NADP 存在时为 0.75 mM。富马酸逆转了 ATP 的抑制作用。在体内，NAD(P)-依赖性苹果酸酶的调节可能会对线粒体 ATP 和富马酸的变化水平做出反应，随着线粒体富马酸浓度的增加，酶经历动力学激活，从而逆转 ATP 对酶的抑制作用。
