MACLURALISIN - A SERINE PROTEINASE FROM FRUITS OF MACLURA-POMIFERA (RAF) SCHNEID

A serine proteinase was isolated from fruits of Maclura pomifera (Raf. ) Schneid. by affinity chromatography on bacitracin-containing sorbent s and gel-filtration. The enzyme, named macluralisin, is a glycoprotei n with a molecular mass of 65 kDa; its protein moiety corresponds to a molecular mass of 50 kDa. The substrate specificity of macluralisin t owards synthetic peptides and insulin B-chain is similar to that of cu cumisin, a subtilisin-like proteinase from melon fruit. The enzyme is completely inhibited by diisopropylfluorophosphate. Its amino-acid com position resembles that of a serine proteinase isolated from the Cucur bitaceae. The N-terminal sequence has 33% of its residues identical to those of the sequence of fungal subtilisin-like proteinase K. Hence, Maclura pomifera serine proteinase belongs to the subtilisin family, w hich seems to be broadly distributed in the plant kingdom.