A Pyrrolidonecarboxylate Peptidase from the Particulate Fraction of Klebsiella cloacae

A pyrrolidonecarboxylate peptidase (EC 3.4.11.8) was purified from the particulate fraction of Klebsiella cloacae. It was demonstrated that the purified enzyme liberates the pyrrolidonecarboxylyl moiety from proteins and peptides, including l-pyrrolidonecarboxylyl-l-proline. The enzyme was solubilized with sodium deoxycholate and purified approximately 1,200-fold with an over-all yield of 16%. The purified enzyme has a molecular weight of approximately 74,000, a pH optimum of 7.0, and a Km of 0.4 mm for p-(lpyrrolidin-2-one-5-carboxamido)benzoic acid, a convenient aqueous-soluble substrate developed for assay of the enzyme. A new method is reported for the identification of 2-pyrrolidone-5-carboxylic acid released from peptides and proteins dependent upon its hydrolytic conversion into glutamic acid.