Structural and kinetic studies on beta-lactamase K1 from Klebsiella aerogenes.
beta-Lactamase K1 from Klebsiella aerogenes 1082E hydrolyses both penicillins and cephalosporins comparably and is inhibited by mercurials but not by cloxacillin. These properties distinguish it from those other beta-lactamases that have been allotted to classes on the basis of their amino sequences. beta-Lactamase K1 has been isolated by affinity chromatography; its composition shows resemblances to class A beta-lactamases. Moreover, the N-terminal sequence is similar to those of class A beta-lactamases: there is about 30% identity over the first 32 residues. Furthermore, a putative active-site octapeptide has been isolated and its sequence is similar to the region around the active-site serine residue in class A beta-lactamases. There is one thiol group in beta-lactamase K1; it is not essential for activity. The pH-dependence of kcat. and kcat./Km for the hydrolysis of benzylpenicillin by beta-lactamase K1 were closely similar, suggesting that the rate-determining step is cleavage of the beta-lactam ring.
D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D001665:Binding Sites; D006863:Hydrogen-Ion Concentration; D007527:Isoenzymes / Q000378:metabolism*; D007700:Kinetics; D007711:Klebsiella pneumoniae / Q000201:enzymology*; D010405:Penicillinase / Q000378:metabolism*; D011489:Protein Denaturation; D013379:Substrate Specificity
D000596:Amino Acids; D007527:Isoenzymes; D010405:Penicillinase