Purification and characterization of the serine endopeptidase from Paecilomyces farinosus

Abstract

A protease was purified from the culture filtrate of a plant worm, Paecilomyces farinosus. The activity of the protease was suppressed by serine protease inhibitors such as phenylmethylsulfonylfluoride (PMSF), chymostatin, and N-tosyl-L-phenylalanine chloromethyl ketone (TPCK). Its molecular mass was estimated to be 28 kDa by SDS-PAGE, and its optimal pH and temperature were pH 8.0 and 45℃, respectively. The cDNA encoding the mature serine protease was cloned by a PCR-based method. The mature serine protease sequence consists of 849 bp, encoding 283 amino acid residues. The amino acid sequence shares sequence homology with subtilisin-type serine endopeptidases belonging to the peptidase S8 family from Beauveria bassiana and Metarhizium anisopliae. This result suggested that the enzyme from P. farinosus is a subtilisin-type serine endopeptidase.