-Lactamases are one of the major causes of antibiotic resistance in Gram negative bacteria.The continuing evolution of
-lactamases that are capable of hydrolyzing our most potent
-lactams presentsa vexing clinical problem, in particular since a number of them are resistant to inhibitors. The efficientinhibition of these enzymes is therefore of great clinical importance. Building upon our previous structuralstudies that examined tazobactam trapped as a
trans-enamine intermediate in a deacylation deficient SHVvariant, we designed a novel penam sulfone derivative that forms a more stable
trans-enamine intermediate.We report here the 1.28 Å resolution crystal structure of
wt SHV-1 in complex with a rationally designedpenam sulfone, SA2-13. The compound is covalently bound to the active site of
wt SHV-1 similar totazobactam yet forms an additional salt-bridge with K234 and hydrogen bonds with S130 and T235 tostabilize the
trans-enamine intermediate. Kinetic measurements show that SA2-13, once reacted with SHV-1
-lactamase, is about 10-fold slower at being released from the enzyme compared to tazobactam. Stabilizingthe
trans-enamine intermediate represents a novel strategy for the rational design of mechanism-basedclass A
-lactamase inhibitors.
