Trypsin‐like hatching protease from mouse embryos: Evidence for the presence in culture medium and its enzymatic properties

Abstract
Enzymatic properties of a protease involved in hatching of mouse embryos were examined. A trypsin-like protease, which most efficiently hydrolyzed t-butoxycarbonyl-Leu-Ser-Thr-Arg-4-methylcoumaryl-7-amide, was demonstrated in culture medium of mouse hatching embryos. The enzyme was strongly inhibited by diisopropyl fluorophosphate, phenylmethanesulfonyl fluoride, leupeptin, antipain, Nα-tosyl-l-lysyl-chloromethane, soybean trypsin inhibitor, and Trasylol, but not or weakly inhibited by p-chloromercuribenzoic acid, EDTA, E-64, pepstain, chymostatin, and bestatin, suggesting a trypsin-like serine proteinase. The protease activity in the medium gradually elevated during the course of hatching, whereas the embryo-associated activity showed no significant change. Furthermore, pyroglutamyl-Leu-argininal, the strongest inhibitor for the enzyme among peptidyl argininals, all of which are potent trypsin inhibitors, showed the strongest inhibition toward hatching. Thus, a trypsin-like protease secreted from hatching embryos into the culture medium may participate in mouse hatching, probably as a hatching enzyme.