Purification and molecular characterization of glutamyl endopeptidase from zein-utilizing Bacillus pumilus strain MS-1

Abstract

In this study, we report the purification and characterization of the extracellular protease BPP-B from the zein-utilizing Bacillus pumilus strain MS-1. The purified BPP-B exhibited glutamyl endopeptidase activity. The Optimum pHs for the cleavage of casein and Suc-Ala-Ala-Pro-Glu-pNA were 11.0 and 8.0, respectively. The bppB gene encoded a 303-amino-acid pre-pro form of BPP-B, and mature BPP-B contained 215-amino-acid residues. BPP-B had three V8 serine protease family signatures (amino acid residues 96-113, 120-137, and 211-224), a serine protease (trypsin or chymotrypsin) family signature (amino acid residues 120-136), and the catalytic triad of serine proteases (His135, Asp186 and Ser259). These results indicate that BPP-B is a glutamyl endopeptidase belonging to peptidase family S2B. This is the first report on a glutamyl endopeptidase from a Bacillus pumilus strain. Although we have recently reported a subtilisin-like protease (BPP-A) playing a major part in zein degradation by Bacillus pumilus strain MS-1, it is possible that BPP-B is also involved in the further digestion of zein.