1. 1. 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. 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°C) with an Ea of 23.5 kJ/mol and a Q10 of 1.34. 3. 3. The apparent Km values for the substrates were 6.5 µM for NADP+, 56 µM for Mg2+, 87 µM for Mn2+ and 4.2 and 73.5 µM for the complexes Mg-isocitrate and Mn-isocitrate, respectively. The physiological significance of these results is discussed. 4. 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. © 1989.
|Number of pages||6|
|Journal||Comparative Biochemistry and Physiology Part B: Comparative Biochemistry|
|Publication status||Published - 1989|