Properties of Sepharose-bound beta-lactamase from Enterobacter cloacae

beta-Lactamase from Enterobacter cloacae P99 was immobilized onto Sepharose by the cyanogen bromide activation method and the properties of the Sepharose-bound enzyme were compared with those of soluble and cell-bound enzyme. The immobilized beta-lactamase showed enhanced stability to storage at 4 degrees C (approximately 1 year) in respect to the free enzyme in solution (few days). The optimum pH for activity is similar for both Sepharose- and cell-bound beta-lactamase and extends over a broader pH range (pH 6-9) than the soluble enzyme (pH 8-9). Immobilization leads also to significant enhancement of thermal stability. Effective enzyme inhibition by flucloxacillin occurs with both soluble and Sepharose-bound beta-lactamase, whereas the cell-bound enzyme is much less (10(-5) times) inhibited. These results indicate that immobilized beta-lactamase could be usefully employed as a tool for investigating the properties of newly designed beta-lactamase inhibitors.