title: The pH-dependence of class B and class C beta-lactamases.
abstract: The classification by structure allots beta-lactamases to (at present) three classes, A, B and C. The pH-dependence of the kinetic parameters for class B and class C have been determined. They differ from each other and from class A beta-lactamases. The class B enzyme was beta-lactamase II from Bacillus cereus 569/H/9. The plots of kcat against pH for the hydrolysis of benzylpenicillin by Zn(II)-requiring beta-lactamase II and Co(II)-requiring beta-lactamase II were not symmetrical, but those of kcat/Km were. A similar feature was observed for the hydrolysis of both benzylpenicillin and cephalosporin C by a class C beta-lactamase from Pseudomonas aeruginosa. The results have been interpreted by a scheme in which two ionic forms of an intermediate can give product, but do so at differing rates.
mesh_terms: D002510:Cephalosporinase / Q000378:metabolism; D002511:Cephalosporins / Q000378:metabolism; D003035:Cobalt / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007527:Isoenzymes / Q000378:metabolism*; D007700:Kinetics; D010400:Penicillin G / Q000378:metabolism; D011549:Pseudomonas / Q000201:enzymology; D015032:Zinc / Q000494:pharmacology; D001618:beta-Lactamases / Q000378:metabolism*
chemical_list: D002511:Cephalosporins; D007527:Isoenzymes; D003035:Cobalt; C025163:cephalosporin C; D002510:Cephalosporinase; D001618:beta-Lactamases; D015032:Zinc; D010400:Penicillin G