DD-carboxypeptidase and peptidoglycan transpeptidase from Pseudomonas aeruginosa

Peptidoglycan transpeptidase and dd-carboxypeptidase have been detected in isolated membranes of Pseudomonas aeruginosa. Cephalosporins and penicillins fail to inhibit the transpeptidase at concentrations as high as 100 mug/ml. dd-Carboxypeptidase, on the other hand, is sensitive to inhibition by beta-lactam antibiotics. The presence of dimethyl sulfoxide in the reaction mixture results in a twofold stimulation of peptidoglycan formation, whereas dd-carboxypeptidase is inhibited approximately 30%. Maximum stimulation of transpeptidase occurs in the presence of both dimethyl sulfoxide and a beta-lactum antibiotic. This is in sharp contrast to the transpeptidase from Escherichia coli, which is sensitive to inhibition by penicillins and cephalosporins.