Changes in activity of cytochrome oxidase during adaptation of goldfish to different temperatures

Abstract

1. 1. Cytochrome oxidase from muscle of goldfish showed an increased activity with gold acclimation and decreased activity with warm acclimation when measured at an intermediate temperature. Activity of t he enzyme from 5°C fish was three to five times greater than from 30° fish when measured 15°. 2. 2. Measurements at various temperatures showed a translation toward the left of the rate-temperature curves with cold acclination. The Q 10 over the linear range was 2·1 for enzyme preparations from fish acclimated to 5, 15, 25 or 30°. 3. 3. Enzyme activity measured at the temperatures of acclimation was maximal at 25°. 4. 4. After 2 hr of heating at 45° the cytochrome oxidase was 80 per cent inactivated, irrespective of acclimation temperature. 5. 5. After 5–10 min of heat treatment, the activity of the enzyme from 5° fish was higher than its activity without heating, decline in activity of enzyme from 15° fish was delayed, but activity from fish acclimated to 25–30° declined directly. 6. 6. It is concluded that cold acclimation causes an increase and warm acclimation a decrease in amount of cytochrome oxidase in goldfish muscle, also that in cold acclimation there is either an increase in a heat-sensitive inhibitor or a change which causes prolongation of thermal activation.