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Characterization of Extracellular β-Lactamases from Penicillin G-Resistant Cells of Streptococcus thermophilus

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In this study, biochemical properties of two extracellular β-lactamases produced by penicillin-resistant Streptococcus thermophilus cells were investigated. Both β-lactamases showed specificity for penicillins but not for cephaloridins. The β-lactamases exhibited different affinities for penicillin G. The one with the higher molecular weight (FI) had a K m value of 3.44 μM and a V max value of 8.33 μmol/min/mg of protein, whereas the β-lactamase with the lower molecular weight (FH) had a K m value of 4.76 μM and a V max value of 3.13 μmol/min/mg of protein. Both β-lactamases were inhibited by iodine, copper sulfate, and iron sulfate but not by EDTA. The optimal pH ranged between 6 and 7, and the optimal temperatures were between 40 and 45°C for both enzymes.

Document Type: Research Article

Affiliations: 1: Department of Food Engineering, Middle East Technical University, 06531 Ankara, Turkey 2: Biology Department, Middle East Technical University, 06531 Ankara, Turkey

Publication date: July 1, 1998

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