Purification and Biochemical Properties of Beta-Lactamase from Escherichia Coli

A β-lactamase was purified to homogeneity from a clinical isolate of Escherichia coli by filtration on Sephadex G-75 and chromatofocusing on a polybuffer exchanger PBE94 column followed by chromatography on phenyl-Sepharose CL-4B. Although the purified enzyme is from a gram-negative bacterial source. it presented several common features of the gram-positive bacterial β-lactamases. After punfication. a single polypeptide with molecular size of 30,000 was found in sodium dodecylsulfate-polyacrylamide gel electrophoresis and enzyme activity that migrated at an isoelectric point of 5.4 was inhibited by clavulanic acid, but not by aztreonam, EDTA and NaCl.