Simple assay and extraction of periplasmic penicillinase in Escherichia coli

Abstract
Benzylpenicillin was clearly separated from benzylpenicilloic acid by ascending chromatography on DEAE cellulose paper using 0.1 M ammonium acetate as a solvent. Using this chromatographic system, penicillinase was assayed by measuring the formation of [14C]benzylpenicilloic acid from [14C]benzylpenicillin. This assay remedies the lack of specificity of the commonly used iodometric assays. Periplasmic penicillinase was released from E. coli by suspension in a mixture of 1% phenethyl alcohol and 5 mM EDTA (pH 7.0). This simple extraction method facilitates the assay of penicillinase in an E. coli culture and will be useful for large-scale purification of periplasmic penicillinase.