Production and Characterization of Extracellular $\beta$-Lactamase from Streptomyces aureofaciens SMF14

A strain SMF14 producing an extracellular $\beta$-lactamase was isolated from soil and identified to be a strain of Streptomyces aureofaciens. $\beta$-Lactamase was purified from the cell free culture broth through batchwise hydroxyapatite adsorption, anion exchange chromatography on DEAE Sephadex A-50, gel filtration on Sephadex G-75, and adsorption chromatography on hydroxyapatite. The molecular mass was estimated to be about 43 kDa by SDS-PAGE. The $\beta$-lactamase had substrate specificity to penicillins and it was inhibited by clavulanic acid, being classified to the group 2a of penicillinase.. The optimal reaction pH and temperature were pH 6.0~7.5 and $50^{\circ}C$. The $K_m, and V_{max}$ values of $\beta$-lactamase for penicillin G were calculated to be 1.72 mM and 5.4$\times$$10^5 \mu M \cdot min^{-1}$, respectively.