Three class-D beta-lactamases (OXA2, OXA1 and PSE2) were produced and purified to protein homogeneity. 6 beta-Iodopenicillanate inactivated the OXA2 enzyme without detectable turnover. Labelling of the same beta-lactamase with 6 beta-iodo[3H]penicillanate allowed the identification of Ser-70 as the active-site serine residue. In agreement with previous reports, the apparent M(r) of the OXA2 enzyme as determined by molecular-sieve filtration, was significantly higher than that deduced from the gene sequence, but this was not due to an equilibrium between a monomer and a dimer. The heterogeneity of the OXA2 beta-lactamase on ion-exchange chromatography contrasted with the similarity of the catalytic properties of the various forms. A first overview of the enzymic properties of the three ‘oxacillinases’ is presented. With the OXA2 enzyme, ‘burst’ kinetics, implying branched pathways, seemed to prevail with many substrates.
Research Article| June 01 1993
A comparative study of class-D β-lactamases
J Van Beeumen;
Biochem J (1993) 292 (2): 555–562.
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P Ledent, X Raquet, B Joris, J Van Beeumen, J M Frère; A comparative study of class-D β-lactamases. Biochem J 1 June 1993; 292 (2): 555–562. doi: https://doi.org/10.1042/bj2920555
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