Inhibitory Effects of Ofloxacin and Cefepime on Enzyme Activity of 6-Phosphogluconate Dehydrogenase from Chicken Liver

In this study, effects of some antibiotics, namely, ofloxacin, cefepime, cefazolin, and ampicillin on the in vitro enzyme activity of 6-phosphogluconate dehydrogenase have been investigated. For this purpose, 6-phosphogluconate dehydrogenase was purified from chicken liver 535-fold with a yield of 18% by using ammonium sulphate precipitation, 2',5'-ADP Sepharose 4B affinity chromatography, and Sephadex G-200 gel filtration chromatography. In order to check the purity of the enzyme, SDS polyacylamide gel electrophoresis (SDS-PAGE) was performed. This analysis revealed a highly pure enzyme band on the gel. Among the antibiotics, ofloxacin and cefepime exhibited inhibitory effects, but cefazolin and ampicillin showed neither important inhibitory nor activatory effects on the enzyme activity. The measured I50 values by plotting activity percent vs. inhibitor concentration, [I50] were 0.1713 mM for ofloxacin and 6.0028 mM for cefepime. Inhibition constants, Ki, for ofloxacin and cefepime were also calculated as 0.2740 ± 0.1080 mM and 12.869 ± 16.6540 mM by means of Lineweaver-Burk graphs, and inhibition types of the antibiotics were found out to be noncompetitive and competitive, respectively. It has been understood from the calculated inhibitory parameters that the purified chicken enzyme has been quite inhibited by these two antimicrobials.