ACTIVE-SITE PEPTIDE OF BETA-LACTAMASE FROM SHIGELLA-FLEXNERI UCSF-129

The peptide containing the catalytic serine of beta-lactamase from Shi gella flexneri was determined as V-D-E-R-F-P-M-M-S-T-F-K. It is a loc al pathogenic strain which produces intestinal problems, especially in children. The highly purified enzyme was prepared by affinity chromat ography on phenylboronic acid-agarose gels. The peptide was obtained b y tryptic hydrolysis, with further purification by Bio-Gel P-4, Sephad ex QAE-25 and Sephadex SP-25. The relevance of the serine, lysine and arginine residues was mainly shown by the loss of enzymatic activity a fter specific chemical modifications. Finally, this enzyme was classif ied as A, according to the similarity of this peptide with that of cla ss A beta-lactamases such as R-TEM 1 and 2.