Relationship between the temperature preferenda of fishes, amphibians and reptiles, and the substrate affinities of their trypsins

Abstract

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 Km(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 Km(app) in its preferred range of temperature. On the other hand, in fish, and in tadpoles ofRana temporaria, Km is independent of experimental temperature over a wide range.