ISOLATION AND CHARACTERIZATION OF OVOCHYMASE, A CHYMOTRYPSIN-LIKE PROTEASE RELEASED DURING XENOPUS-LAEVIS EGG ACTIVATION

A chymotrypsin-like protease contained in the perivitelline space of u nactivated Xenopus eggs is released during egg activation and appears to participate in vitelline envelope conversion. This 30-kDa protease, which we have termed ovochymase, was isolated from the exudate of act ivated eggs using a soy bean trypsin inhibitor-agarose affinity column . The column eluant contained only two proteins, the 30-kDa ovochymase plus a 78-kDa chymotrypsinlike proteolytic activity. The 78-kDa prote ase was not usually observed in fresh egg exudate samples and thus was activated during the purification process and may represent the propo sed precursor of the 30-kDa protease. The 30- and 78-kDa proteases wer e separated by gel filtration HPLC or by SDS-PAGE. The N-terminal amin o acid sequence of SDS-PAGE-isolated ovochymase was determined to be V VGGQQAAPR. This conserved amino acid sequence, plus active site specif ic inhibition and substrate specificity studies, places ovochymase in the serine protease I family of enzymes. A two-dimensional protease ac tivity gel revealed that ovochymase is present as several isozymes wit h a wide range of pl's. (C) 1995 Academic Press, Inc.