[Serine proteinases of lower vertebrates].

Recent data on the effect of serine proteinases of lower vertebrates are generalized. Hydrolysis specificity and kinetics of different synthetic substrates, dependence of the activity of enzymes on pH, their irreversible inhibition by chloromethyl ketones of amino acids and peptides as well as high-molecular proteinase inhibitors are considered in detail. The data testify to the fact that chymotrypsins and trypsins of higher vertebrates and serine proteinases of lower vertebrates act as an acid-base catalysis. Enzymes in the pyloric cacca of fishes are in the state of proenzymes and are transformed into an active form with the aid of their own proteolytic factors. The esterase and proteolytic activity of fish proteinases is concentrated in the same active site and reaches the highest values at pH 7,8. New data are presented on particularities of the lower vertebrate proteinases, on the similarity and differences in their specificity. A distinct difference is shown in the nature of the binding site of the active centre in a number of serine proteinases of fishes as compared to chymotrypsin and trypsin of higher vertebrates.