NADP+-isocitrat-dehydrogenase aus Idus idus (Pisces: Cyprinidae). II. Einfluß der temperatur auf substrat- und cosubstrataffinität

Maximum substrate and cosubstrate affinity, as judged by the Michaelis constant (K _M ), of NADP⁺-dependent isocitrate dehydrogenase of pig heart (purchased from Boehringer, Mannheim, FRG) is attained at 37°C. If K _M -values of substrate (Isocitrate, IC) and cosubstrate (NADP⁺) of NADP⁺-dependent isocitrate dehydrogenase (ICDH) of the white dorsal muscle of Idus idus L. is plotted against the experimental temperature (VT), W-shaped curves result. With increasing adaptation temperature (AT), there is a shift to increasing VT. It is suggested that the W-shaped curves are due either to the simultaneous presence of two multiple forms of the enzyme, or to the reversible temperature-dependent interconversion of one protein species.