海洋物种的生化研究——I. 大菱鲆肝脏（Scophthalmus maximus L.）中依赖NADP(+)的异柠檬酸脱氢酶

Biochemical studies in marine species--I. NADP(+)-dependent isocitrate dehydrogenase from turbot liver (Scophthalmus maximus L.).

Munilla-Morán R, Stark J R

Department of Brewing and Biological Sciences, Heriot-Watt University, Edinburgh, Scotland.

Comp Biochem Physiol B. 1989;93(4):823-8. doi: 10.1016/0305-0491(89)90053-9.

Abstract

An NADP+-dependent isocitrate dehydrogenase was extracted from turbot liver. The enzyme required divalent cations (Mg2+ or Mn2+) for its activity but was inhibited by high salt concentrations. 2. The enzyme had an optimum activity in the pH range between 7.5 and 9.0. The enzymic activity increased with temperature (in the range of 5 to 68 degrees C) with an Ea of 23.5 kJ/mol and a Q10 of 1.34. 3. The apparent Km values for the substrates were 6.5 microM for NADP+, 56 microM for Mg2+, 87 microM for Mn2+ and 4.2 and 73.5 microM for the complexes Mg-isocitrate and Mn-isocitrate, respectively. The physiological significance of these results is discussed. 4. The enzyme was inhibited by citrate and adenine nucleotides. The degree of inhibition depended on the relation between the concentrations and that of magnesium. A possible regulating mechanism is proposed.

摘要

从大菱鲆肝脏中提取出一种依赖烟酰胺腺嘌呤二核苷酸磷酸（NADP⁺）的异柠檬酸脱氢酶。该酶的活性需要二价阳离子（Mg²⁺或Mn²⁺），但会受到高盐浓度的抑制。2. 该酶在pH值7.5至9.0范围内具有最佳活性。酶活性随温度升高（在5至68摄氏度范围内）而增加，活化能（Ea）为23.5千焦/摩尔，温度系数（Q10）为1.34。3. 底物的表观米氏常数（Km）值分别为：NADP⁺为6.5微摩尔，Mg²⁺为56微摩尔，Mn²⁺为87微摩尔，Mg - 异柠檬酸和Mn - 异柠檬酸复合物分别为4.2和73.5微摩尔。讨论了这些结果的生理学意义。4. 该酶受到柠檬酸和腺嘌呤核苷酸的抑制。抑制程度取决于它们与镁离子浓度之间的关系。提出了一种可能的调节机制。