Steric Induced Inhibition of Serine β–Lactamase Catalyzed Hydrolysis

Serine lactamases are bacterial enzymes that cause antibiotic resistance by rapid hydrolysis of lactam antibiotics. Development of efficient covalent inhibitors for serine ‐lactamases requires an understanding of the factors that can increase the free energy barrier for hydrolysis of the covalent‐intermediate formed by the lactamases and the ligands. We show that steric factors introduced by methyl substitution at a suitable position in an existing lactam drug can slow down its hydrolysis by sterically hindering the hydrolytic water molecule from approaching the reaction site. Through molecular simulations, we demonstrate that a weak cephalosporin, like cephalothin, can be revitalized with this strategy. An increase in the lifetime of the acyl–enzyme complex leads to the inhibition of serine lactamases.