ISOLATION AND PROPERTIES OF SOME REPTILIAN AND FISH CHYMOTRYPSINS

Chymotrypsinogens were isolated in highly purified form by a chromatographic procedure, from the pancreas of the turtles Chelydra serpentina and Pseudemys elegans. After activation with bovine trypsin, they both hydrolyze the substrate N-benzoyl-l-tyrosine ethyl ester about three times as rapidly as bovine chymotrypsin does. The rates of the inactivations by chloromethyl ketone derivative of l-phenylalanine and l-leucine were measured, on chymotrypsins from three reptiles and the tuna. From these, and from the relative activities on tyrosine and leucine substrates, a partial similarity to procine chymotrypsin C (which shows high rates with leucine derivatives), was discerned. It is therefore concluded that although the reactivity of the chymotrypsin active center is basically similar from the fish to the mammals, complex variations on the basic pattern in relation to the binding site are apparent in each species examined. A clear division into A and C types, as found in mammals, could not be made in the range of lower vertebrates investigated here. The alkylation and specificity evidence suggests that forms with combined features of both the A and C types have appeared in reptilian and fish species. © 1969.