Characterization and molecular cloning of a glutamyl endopeptidase from Staphylococcus epidermidis

A novel extracellular endopeptidase, designated GluSE, was purified from Staphylococcus epidermidis ATCC 14990 cultured by the dialysis membrane technique, and the structural gene (gseA) was cloned. GluSE was a 27kDa, glutamic acid-specific protease, and the optimal pH was 8.0. The proteolytic activity was specifically inhibited with diisopropyl fluorophosphate, indicating that it is a serine protease. The gseA encoded a single polypeptide of 282 amino acids with a deduced molecular weight of 30,809, in which the first 19 N-terminal amino acids completely matched the deduced sequence starting at Val-67, suggesting that GluSE is synthesized with a propeptide. The amino acid sequence of GluSE exhibited 50.5% identity to Staphylococcus aureus V8-protease (GluV8). Although GluSE lacks a C-terminal 12 repeats of the PBN/PBZ tripeptide of GluV8, a catalytic triad of His-117, Asp-159 and Ser-235 was conserved in GluSE. Southern hybridization analysis revealed that gseA exists as a single copy on the chromosomal DNA. The finding that production of GluSE was obviously observed in the adherent culture conditions of the dialysis membrane technique, but not in the planktonic culture conditions, strongly suggests that GluSE could be involved in an important etiologic process in S.epidermidis infection leading to multiple tissue damages.