title: Properties of a class C beta-lactamase from Serratia marcescens.
abstract: A beta-lactamase produced by a penicillin-resistant strain of Serratia marcescens was isolated and purified. The kcat. value for benzylpenicillin was about 5% of that observed for the best cephalosporin substrates. However, the low Km of the penam resulted in a high catalytic efficiency (kcat./Km) and the classification of the enzyme as a cephalosporinase might not be completely justified. It also exhibited a low but measurable activity against cefotaxime, cefuroxime, cefoxitin and moxalactam. Substrate-induced inactivation was observed both with a very good (cephalothin) or a very bad (moxalactam) substrate. The active site was labelled by beta-iodopenicillanate. Trypsin digestion produced a 19-residue active-site peptide whose sequence clearly allowed the classification of the enzyme as a class C beta-lactamase.
mesh_terms: D000596:Amino Acids / Q000032:analysis; D001426:Bacterial Proteins; D001665:Binding Sites; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009994:Osmolar Concentration; D010446:Peptide Fragments / Q000032:analysis; D012706:Serratia marcescens / Q000201:enzymology*; D001618:beta-Lactamases / Q000302:isolation & purification* / Q000378:metabolism
chemical_list: D000596:Amino Acids; D001426:Bacterial Proteins; D010446:Peptide Fragments; C048795:AmpC beta-lactamases; D001618:beta-Lactamases