A comparative study of class-D beta-lactamases.
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.
Ledent
P
P
Laboratoire d'Enzymologie, Université de Liège, Belgium.
Raquet
X
X
Joris
B
B
Van Beeumen
J
J
Frère
J M
JM
D001665:Binding Sites; D002384:Catalysis; D002846:Chromatography, Affinity; D002852:Chromatography, Ion Exchange; D003001:Cloning, Molecular; D007700:Kinetics; D010397:Penicillanic Acid / Q000378:metabolism / Q000031:analogs & derivatives; D010957:Plasmids; D012694:Serine / Q000378:metabolism; D013379:Substrate Specificity; D065093:beta-Lactamase Inhibitors; D001618:beta-Lactamases / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*
D065093:beta-Lactamase Inhibitors; D012694:Serine; D010397:Penicillanic Acid; C031528:6-iodopenicillanic acid; D001618:beta-Lactamases