Calcium ions make phytohemagglutinin resistant to trypsin proteolysis.

To investigate the mechanism of phytohemagglutinin (PHA) susceptibility or resistance to the action of proteolytic enzymes, its in vitro proteolysis by trypsin was studied. It was found that Ca (2+) gives resistance to the native PHA molecule to trypsin proteolysis. In the absence of Ca (2+) trypsin performs a thorough hydrolysis of PHA.

Applying the increase in rate constants of cooperative proteolysis to the determination of transition curves of protein denaturation.

The transition curves of soybean glycinin egg lysozyme, bovine serum albumin (BSA) denaturation under the action of increasing urea concentration were monitored by determination of the increase in rate constants of cooperative enzymatic proteolysis. The results were compared with those obtained using intrinsic fluorescence and the number of accessible tyrosine. It was shown that the determination of the changes of proteolysis rate permits to disclose conformation changes not detected by other methods.