The effect of temperature acclimation upon succinic dehydrogenase activity from the epaxial muscle of the common goldfish (Carassius auratus L)-I. Properties of the enzyme and the effect of lipid extraction

Abstract

1. 1. Succinic dehydrogenase actuvity from the epaxial muscle of 5°C-acclimated goldfish was 1·3-2·2 times (depending upon season) that of 25°C-acclimated goldfish when measured at the same temperature in both crude homogenates and isolated mitochondrial fractions. 2. 2. Lipid extraction (formation of an acetone powder)_ of the particulate enzyme resulted in a three- to fourfold drop in specific activity, a reduction in the Ea and a reduction in the absolute Km values for succinate. 3. 3. Electrophoresis of soluble preparations from both 5- and 25°C-acclimated goldfish yielded a single SDH band of identical electrophoretic mobility from each acclimation group. 4. 4. Kinetics studies revealed that the Km for PMS was temperature independent and did not vary with acclimation temperature; particulate and soluble preparations were characterized by identical Km values for PMS. 5. 5. There was a direct reltionship between the Km for succinate and the assay temperature in both soluble and particulate preparations which was identical for both acclimation groups; the magnitude of the Km temparature response was reduced by lipid extraction. 6. 6. Inhibition of the soluble enzyme by oxaloacetic acid was extremely temperature dependent as evidenced by a twelve- to fifteenfold increase in i upon a drop in assay temperature from 25 to 5°C. 7. 7. Goldfish SDH† was characterized by a very steep pH-activity profile in the physiological range. 8. 8. Ea measurements suggested a positive correlation between habitat temperature and activation energy. 9. 9. These results were interpreted as indicating that SDH normally functions as a lipoprotein complex within the inner mitochondrial membrane and exhibits properties which maintain temperature-independent catalytic function in response to short-term and prolonged temperature fluctuations. © 1972.