The Temperature Dependence of Myosin-adenosinetriphosphatase and Alkaline Phosphatase in Lizards.

Abs t r ac t -1 . The temperature dependence of myosin ATP-ase and intestinal alkaline phosphatase from a variety of lizards having distinct preferred temperatures was compared. 2. The ATP-ase was relatively thermolabile; reductions in activity at temperatures above the optimum resulted primarily from irreversible denaturation. However, pronounced differences were evident in both the optimal temperatures and thermostabilities of the ATP-ases from eight species of lizards. Optima ranged from 33-42°C. 3. Alkaline phosphatase was more heat resistant and reductions in activity above the optimum were largely reversible. There was virtually no difference in the temperature dependence of the alkaline phosphatase from four species studied. The optimal temperature for this enzyme was about 42°C and no denaturation was evident at 51°C. 4. Differences in the temperature dependence of the ATP-ase correlated well with differences in the preferred temperatures of the respective species. Thus, biochemical adjustments in ATP-ase appear to be closely associated with thermal adaptations evident at the level of the whole animal ; but it is clear that not all enzymes are similarly involved in organismal thermal adjustments.