Autoproteolysis in human seminal plasma under acidic condition

The existence of both neutral and acidic proteases in human seminal plasma suggests a possible autohydrolysis of the proteins in the fluid. By means of polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate, the autoproteolysis in human seminal plasma was shown to occur at pH 3.5 but not at pH 5.0--7.5 conditions. At pH 3.5, most proteins of large molecular weight, except one of 28,000 daltons, were completely hydrolyzed into peptides of 13,000 daltons or smaller. The autoproteolysis was due to the action of the acidic protease since it can be blocked by 1 mM of p-bromophenacyl-bromide or 1,2-epoxy-3-(p-nitrophenoxy) propane, the specific inhibitors of the acidic protease.