In Vitro Effects of Some Antibiotics on Glutathione Reductase from Sheep Liver

The effects of gentamicin sulphate, thiamphenicol, ofloxacin, levofloxacin, cefepime, and cefazolin were investigated on the in vitro enzyme activity of glutathione reductase. The enzyme was purified 1,850-fold with a yield 18.76% from sheep liver using ammonium sulphate precipitation, 2′, 5′-ADP Sepharose 4B affinity chromatography, and Sephadex G-200 gel filtration chromatography. The purified enzyme showed a single band on sodium dodecyl sulfate polyacrilamide gel electrophoresis (SDS-PAGE). The enzyme activity was measured spectrophotometrically at 340?nm, according to the method of Carlberg and Mannervik. From these six antibiotics, Ofloxacin, levofloxacin, cefepime, and cefazolin inhibited the activity of the purified enzyme; gentamicin sulphate and thiamphenicol showed little effect on the enzyme activity. The I50 values for these four antibiotics were 0.150?mM, 0.154?mM, 3.395?mM, and 18.629?mM, respectively. The Ki constants were 0.047±0.034?mM, 0.066±0.038?mM, 4.885±3.624?mM, and 6.511±1.894?mM, respectively and they were competitive inhibitors.