Engineering a novel β-Iactamase by a single point mutation

摘要: beta-Lactamases are widespread and efficient bacterial enzymes which play a major role in resistance to penicillins cephalosporins. In order elucidate the of residues lying conserved loop enzymatic cavity active-site serine Streptomyces albus G beta-lactamase, modified proteins were produced by oligo-directed mutagenesis. Mutation Asn116, lies on one side active site pointing substrate-binding site, into residue resulted spectacular modifications specificity profile enzyme. That replacement yielded an enzyme with nearly unchanged activity towards good penicillin substrates. sharp contrast its efficiency hydrolysing cephalosporins was drastically reduced, best substrates suffering largest decrease second-order rate constant for acylation. fact that single mutation generated truly new behaving exclusively as penicillinase, situation is never encountered same degree any numerous naturally occurring variants class A beta-lactamases.