Relationship between the Temperature Preferenda of Fishes Amphibians and Reptiles, and the Substrate Affinities of Their Trypsins

Summary

The apparent Michaelis constants of crude trypsin preparations of three fishes with stomach, four Cyprinidae, five amphibians and three reptiles were determined at 15^°C, 30^°C and at the temperature preferendum of each species. The affinity of the sum of all trypsin isozymes of a given species for DL-BAPA was correlated with the temperature preferenda (Tp) of the species. The affinity of trypsins in vertebrates with a high Tp is, as a rule, lower than in species with a low Tp. However, the agastric cyprinids possess trypsins with a much higher affinity than those of other vertebrates. Within species the relationship between K_m(app) and experimental temperature is different in different groups of vertebrates. In the terrestrial species there is a tendency for each species to have the lowest value of K_m(app) in its preferred range of temperature. On the other hand, in fish, and in tadpoles of Rana temporaria, K_m is independent of experimental temperature over a wide range.