Substrate spectrum extension of PenA in Burkholderia thailandensis with a single amino acid deletion, Glu168del.

We describe a deletion mutation in a class A β-lactamase, PenA, of Burkholderia thailandensis that extended the substrate spectrum of the enzyme to include ceftazidime. Glu168del was located in a functional domain called the omega loop causing expansion of the space in the loop, which in turn increased flexibility at the active site. This deletion mutation represents a rare but significant alternative mechanical path to substrate spectrum extension in PenA besides more common substitution mutations.