Structure and function of an isozyme of earthworm proteases as a new biocatalyst

The amino acid sequence of the earthworm-serine protease, isozyme C, which shows not only elastase-like activity but also trypsin-like activity, was determined. The catalytic triad of the trypsin family, His, Asp, Ser, was conserved in isozyme C, but the primary substrate determinant of trypsin, Asp, was missing in isozyme C, the same as in elastase. One of the two Gly at the entrance of the substrate-binding pocket of trypsin was replaced by Val as in elastase, however, the other was replaced by Ser whereas Thr is present in elastase. Furthermore, isozyme C also showed esterase-like activity, which was applicable for the synthesis of useful substances.