Identification of Products of Inhibition of GES-2 β-Lactamase by Tazobactam by X-ray Crystallography and Spectrometry

The GES-2 beta-lactamase is a class A carbapenemase, the emergence of which in clinically important bacterial pathogens is a disconcerting development as the enzyme confers resistance to carbapenem antibiotics. Tazobactam is a clinically used inhibitor of class A beta-lactamases, which inhibits the GES-2 enzyme effectively, restoring susceptibility to beta-lactam antibiotics. We have investigated the details of the mechanism of inhibition of the GES-2 enzyme by tazobactam. By the use of UV spectrometry, mass spectroscopy, and x-ray crystallography, we have documented and identified the involvement of a total of seven distinct GES-2 center dot tazobactam complexes and one product of the hydrolysis of tazobactam that contribute to the inhibition profile. The x-ray structures for the GES-2 enzyme are for both the native (1.45 angstrom) and the inhibited complex with tazobactam (1.65 angstrom). This is the first such structure of a carbapenemase in complex with a clinically important beta-lactam inhibitor, shedding light on the structural implications for the inhibition process.