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Accueil > Publications > Recherche par années > Années 1990 > 1991

Brannigan, J ; Matagne, A ; Jacob, F ; Damblon, C ; Joris, B ; Klein, D ; Spratt, Bg ; Frère, JM

The mutation Lys234His yields a class-a ß-lactamase with a novel pH-dependence

Biochemical Journal 278 673-678

par Administrateur - publié le

Abstract :

The lysine-234 residue is highly conserved in ß-lactamases and in nearly all active-site-serine penicillin-recognizing enzymes. Its replacement by a histidine residue in the Streptomyces albus G class A ß-lactamase yielded an enzyme the pH-dependence of which was characterized by the appearance of a novel pK, which could be attributed to the newly introduced residue. At low pH, the k(cat.) value for benzylpenicillin was as high as 50 % of that of the wild-type enzyme, demonstrating that an efficient active site was maintained. Both k(cat.) and k(cat.)/K(m) dramatically decreased above pH 6 but the decrease in k(cat.)/K(m) could not be attributed to larger K(m) values. Thus a positive charge on the side chain of residue 234 appears to be more essential for transition-state stabilization than for initial recognition of the substrate ground state.