Interaction of clavulanate with the β-lactamases of Streptomyces albus G and Actinomadura R39

The reactions of beta-lactamases of Actinomadura R39 and Streptomyces albus G with clavulanate proceed along branched pathways. Both enzymes perform the hydrolysis of this beta-lactam with rather high efficiencies (kcat. = 18s-1 and 52s-1 respectively). If large clavulanate/enzyme ratios are used, complete inactivation of the enzymes is observed. At lower ratios, inactivation is only partial. Irreversible inactivation occurs after 400 and 20000 turnovers for the A. R39 and S. albus G enzymes respectively. With the A. R39 beta-lactamase, a transiently inhibited complex is also formed that remains undetectable with the S. albus G beta-lactamase. Kinetic models are presented and studied for the interaction between clavulanate and both enzymes. A tentative general reaction scheme is also discussed.