Inhibitory effects of some drugs on hepatic glucose 6-phosphate dehydrogenase from Lake Van fish (chalcalburnus tarischii pallas, 1811) were investigated. For this purpose, initially liver glucose 6-phosphate dehydrogenase was purified 899-fold in a yield of 46.24% by using 2',5'-ADP Sepharose 4B affinity gel. In order to control the purification of enzyme was done SDS polyacrylamide gel electrophoresis. SDS polyacrylamide gel electrophoresis showed a single band for enzyme. A constant temperature (+4'C) was maintained during the purification process. Enzyme activity was determined with the Beutler method by using a spectrophotometer at 340 nm. Vankomycine, sulfanylamide, sulfanylacetamide, nidazole, ciprofloxacin, amoxicillin and KMn04 were used as drugs. These drugs exhibited inhibitory effects on the enzyme. IC50 values of vankomycine, sulfanylamide, sulfanylacetamide, nidazole, ciprofloxacin, amoxicillin and KMn04 were 1.88, 0.037, 0.032, 1.178, 2.26, 643.5 and 0.0002 mM, and the Ki constants 1. 18 +/- 0.148, 0.119 +/- 0.021, 0.075 +/- 0.015, 1.15 +/- 0.21, 7.69 +/- 0.67, 1007 +/- 69, and 0.001 +/- 0.00022 mM, respectively. While vankomycine and nidazole showed competitive inhibition, others displayed noncompetitive inhibition. K-i constants and IC50 values for drugs were determined by Lineweaver-Burk graphs and plotting activity percentage versus [I], respectively. (C) 2006 Elsevier B.V. All rights reserved.