Salt Effects on Plastein Formation by α-Chymotrypsin

Abstract

The plastein formation by α-chymotrypsin from an ovalbumin hydrolysate was affected in an order of valency of salts when the concentration of each salt was 1M. Monovalent cations were rather effective at this concentration and enhanced the plastein yield by 10%. In the presence of NaCl, the plastein formation showed two distinct maximal rates at its concentrations of 0.1M and 0.8M. The first maximum was considered to be resulted from an increase in enzyme activity, since chymotryptic hydrolysis of both N-acetyl-L-tyrosine ethyl ester and benzyloxycarbonyl-L-phenylalanine p-nitrophenyl ester was activated at an NaCl concentration of 0.1_??_0.2M. The second maximum was ascribed to the salting-out of the product due to the higher concentration of NaCl. A salt-tolerant protease was also used to confirm the above conclusions. It was observed that this enzyme was much effective in producing a plastein at a high NaCl concentration. This may be due to the fact that both the enzyme activation effect and the product salting-out effect participate co-operatively.