Penicillinase-releasing Protease of BaciZZus Zicheniformis 749

The membrane penicillinase ofBacillus licheniformis 7491 C differs from the exopenicillinase in that it has an additional 24 amino acid residues and a phosphatidylserine at the NH* terminus (Yamamoto, S., and Lampen, J. 0. (1976) J. Biol. Chem. 251, 4095-4101). The conversion of the membrane penicillinase to the exo form is probably carried out by a specific penicillinase-releasing protease (PR-protease) whose properties are generally consistent with the properties of.penicillinase secretion. The substrate specificity of the PR-protease was determined by identifying the NH2 and COOH termini of the peptides produced by hydrolysis of ribonuclease B and beef insulin. The enzyme hydrolyzed only peptide bonds involving the carboxyl groups of serine or threonine. Similar bonds in synthetic dior tripeptides of L-serine were not cleaved. The existence of seryl-lysine and threonyl-glutamic acid bonds in the protease-susceptible (phospholipopeptide) region of the membrane penicillinase and the presence of only lysine or glutamic acid at the NH, terminus of the exoenzyme released in uiuo are consistent with the specificity of PR-protease; hence, we propose that this enzyme has an essential role in the formation of exopenicillinase. The PR-protease is a potential tool for protein sequence determination because of its narrow and novel substrate specificity.