Knott-Hunziker V, Petursson S, Waley SG, Jaurin B, Grundström T. The acyl-enzyme mechanism of beta-lactamase action. The evidence for class C Beta-lactamases.
Biochem J 1982;
207:315-22. [PMID:
6818947 PMCID:
PMC1153862 DOI:
10.1042/bj2070315]
[Citation(s) in RCA: 81] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Methanol or ethanol can replace water in the action of certain chromosomal beta-lactamases on benzylpenicillin: the products are alpha-methyl or alpha-ethyl benzylpenicilloate. The beta-lactamases were from a mutant of Pseudomonas aeruginosa 18S that produces the enzyme constitutively [Flett, Curtis & Richmond (1976) J. Bacteriol. 127, 1585-1586; Berks, Redhead & Abraham (1982) J. Gen. Microbiol. 128, 155-159] and from Escherichia coli K12 (the ampC beta-lactamase) [Lindström, Boman & Steele (1970) J. Bacteriol. 101, 218-231]. The variation of the rates of alcoholysis and hydrolysis with concentration of alcohol show that the rate-determining step is breakdown of an intermediate. This intermediate is likely to be the acyl-enzyme. The esters, alpha-methyl or alpha-ethyl benzylpenicilloate, are themselves substrates for the Pseudomonas beta-lactamase, benzylpenicilloic acid being formed. Thus this beta-lactamase can be an esterase. The kinetics for the hydrolysis of cloxacillin by the Pseudomonas beta-lactamase are consistent with the acyl-enzyme, formed by acylation of serine-80, being an intermediate in the overall hydrolysis.
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