Isocitrate Dehydrogenases in Rainbow-trout Liver
نویسندگان
چکیده
1. The kinetics of the thermally induced enzyme variants of the supernatant NADP-isocitrate dehydrogenase from rainbow-trout liver are investigated. 2. Fish acclimatized to 20C (cold-adapted enzyme) and 170C (warm-adapted enzyme) show different relative distributions of the three NADP-isocitrate dehydrogenase isoenzymes; this has been demonstrated with electrophoresis and electrofocusing techniques. 3. Plots ofKm versus temperature for the cold-adapted and warm-adapted enzyme variants are complex in nature with apparent maximal enzyme-substrate affinity corresponding to the temperature at which the trout is acclimatized. Both substrates, DL-isocitrate and NADP+, give similar curves although the magnitude of the Km change with temperature is much decreased in the case of NADP+. 4. Ea values of approx. 18kcal/mol were determined for both the cold-adapted and warm-adapted enzyme variants. 5. In an attempt to determine how velocities can be increased at low temperatures, cation, pH requirements, metabolite and enzyme concentrations were examined. 6. NAD-isocitrate dehydrogenase could not be detected in trout tissues.
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