# Mechanistic basis for inhibition of the extended‐spectrum β‐lactamase GES‐1 by enmetazobactam and tazobactam

## TL;DR

The study explains how enmetazobactam inhibits a key antibiotic resistance enzyme more effectively than tazobactam.

## Contribution

The study reveals a novel mechanism of inhibition by enmetazobactam against the GES-1 enzyme, differing from previous assumptions.

## Key findings

- Enmetazobactam forms different covalent breakdown products with GES-1 compared to tazobactam.
- No lysinoalanine cross-link formation was observed in GES-1 inhibition by enmetazobactam.
- Enmetazobactam is a more potent inhibitor of GES-1 than tazobactam.

## Abstract

β‐Lactamase‐catalysed hydrolysis is the primary form of β‐lactam antibiotic resistance in Gram‐negative bacteria. The penicillanic acid sulfone (PAS) enmetazobactam is thought to inhibit extended‐spectrum β‐lactamases (ESBLs) by fragmentation of an initial acyl‐enzyme to form an active‐site lysinoalanine cross link. We investigate interactions of enmetazobactam and its congener tazobactam with GES‐1, an ESBL with structural features of carbapenem‐hydrolysing β‐lactamases. Crystal structures show different breakdown products of the two inhibitors covalently bound to the catalytic Ser70, assigned using quantum mechanics/molecular mechanics (QM/MM) calculations. We find no evidence for lysinoalanine formation, with mass spectrometry indicating active enzyme regeneration, behaviour previously observed for carbapenem‐hydrolysing enzymes, but not ESBLs. This work establishes that PAS inhibitors interact with diverse β‐lactamases by differing mechanisms, which should inform development of future compounds.

Antimicrobial resistance (AMR) is of huge importance, resulting in over 1 million deaths each year. Here, we describe how a new drug, enmetazobactam, designed to help fight resistant bacterial diseases, inhibits a key enzyme (GES‐1) responsible for AMR. Our data show it is a more potent inhibitor than the related tazobactam, with high‐level computation describing its chemistry on binding.