Comparison of periplasmic and membrane associated beta-lactamase

Beta-lactamase encoded by a plasmid pBR 322 was produced during the active growth phases of Escherichia coli IA 199. The maximal specific activity was about 15 times higher in shock fluid than in the cells disrupted by sonic disintegration. beta-Lactamase activity found in the membrane preparations increased gradually parallel to the cell growth. The amount of beta-lactamase in the membrane fraction, however, was only 0.2-0.4% of that found in shock fluid. beta-Lactamase was purified to homogeneity from shock fluid by a one-step procedure in a DEAE-Sepharose column. Most of the beta-lactamase activity present in the membrane fraction was released by salt extraction. beta-Lactamase solubilized treatment after salt extractions had the same molecular weight and immunological properties as beta-lactamase purified from the periplasmic space. Membrane associated beta-lactamase did not contain any covalently linked phospholipid.