Abstract
A beta-lactamase from culture supernatant of Streptomyces cellulosae was purified about 1,450-fold to apparent homogeneity in polyacrylamide gel electrophoresis and isoelectric focusing on polyacrylamide gel sheet. The methods used were ammonium sulfate precipitation, CM-52 cellulose ion-exchange chromatography and affinity chromatography on Blue Sepharose CL-6B. The molecular weight was determined to be approximately 27,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. This value was in good agreement with the previous value determined by gel filtration on Sephadex G-75. The isoelectric point was pH 9.5. The enzyme behaved primarily as penicillinase and apparent Km value for benzylpenicillin was 500 microM. The beta-lactamase of S. cellulosae interacted strongly with blue dextran and NADP+-agarose but not with Sepharose. In addition, the presence of NADP+ but not NAD+ and ATP diminished sharply the intrinsic fluorescence intensity of the enzyme and the apparent association constant was calculated to be 1.4 x 10(3) M-1. The beta-lactamase decreases its enzymatic activity against benzylpenicillin in the presence of NADP+. From these results, it is suggested that this beta-lactamase has a dinucleotide binding fold.
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