Large-scale purification of the chromosomal beta-lactamase from Enterobacter cloacae P99.

Homogeneous beta-lactamase (beta-lactam hydrolase, E.C. 3.5.2.6) from Enterobacter cloacae P99, an enzyme that has an important function in antibiotic resistance, was prepared using a single cation-exchange chromatographic step with CM-Sepharose fast-flow. A 6-g amount of the enzyme was isolated from 5 kg of cell paste, with 84% of the enzyme activity in the cell homogenate being recovered by the single cation-exchange step. The specific activity of the beta-lactamase was 587 U/mg protein. The relative molecular mass of the enzyme was determined to be 45 kDa by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate and the isoelectric point was 8.95.