CHARACTERIZATION OF THE CLEAVAGE SPECIFICITY OF A SUBTILISIN-LIKE SERINE PROTEINASE FROM OPHIOSTOMA-PICEAE BY LIQUID-CHROMATOGRAPHY MASS-SPECTROMETRY AND TANDEM MS

A proteinase secreted by the sapstaining fungus Ophiostoma piceae is t hought to be necessary for the primary retrieval of nitrogen from wood proteins. By using mass spectrometry (MS) techniques, we have establi shed the cleavage specificity of this subtilisin-like serine proteinas e. This work demonstrated the potential of MS in determining cleavage specificities of newly isolated proteinases in a relatively short time frame, and determined that the O. piceae proteinase showed a substrat e specificity similar to that of proteinase K. Primary cleavage of the insulin B-chain occurred between Leu(15) and Tyr(16). In addition num erous secondary cleavage sites occurred after hydrophobic, polar, and charged amino acids indicating a broad specificity.