Inhibition effects of some antibiotics on the activity of glucose 6-phosphate dehydrogenase enzyme from rainbow trout (Oncorhynchus mykiss Walbaum, 1792) erythrocytes

Inhibitory effects of some antibiotics on glucose 6-phosphate dehydrogenase from the erythrocytes of rainbow trout (Oncorhynchus mykiss Walbaum, 1792) were investigated. For this purpose, initially erythrocyte glucose 6-phosphate dehydrogenase was purified 1271.19-fold in a yield of 70.40% by using ammonium sulfate precipitation and 2',5'-ADP Sepharose 4B affinity gel. A constant temperature (+4 degreesC) was maintained during the purification process. Enzyme activity was determined with the Beutler method by using a spectrophotometer at 340 nm. This method was utilized for all kinetic studies. Thiamphenicol, amikacin, gentamicin, and netilmicin were used as antibiotics. All the antibiotics exhibited inhibitory effects on the enzyme. K-i constants for glucose 6-phosphate dehydrogenase were found by means of Lineweaver-Burk graphs. While thiamphenicol and amikacin showed competitive inhibition, gentamicin and netilmicin displayed noncompetitive inhibition. In addition, I-50 values of the antibiotics were determined by plotting activity % vs. [1].