Purification and characterization of glucose 6-phosphate dehydrogenase enzyme from rainbow trout ( Oncorhynchus mykiss ) liver and investigation of the effects of some metal ions on enzyme activity

Abstract

Glucose 6-phosphate dehydrogenase (d-glucose 6-phosphate: NADP⁺ oxidoreductase, EC 1.1.1.49; G6PD) is a key enzyme that is localized in all mammal tissues, especially in cytoplasmic sections and that catalyzes the first step of pentose phosphate metabolic pathway. In this study, G6PD enzyme was purified 1444-fold with a yield of 77% from rainbow trout liver using 2′,5′-ADP-sepharose-4B affinity chromatography. Moreover, a purity check of the enzyme was performed with sodium dodecyl sulfate–polyacrylamide gel electrophoresis. Some characteristic features like optimal pH, stable pH, optimal temperature and optimal ionic strength were determined for the purified enzyme. In addition to this, in vitro effects of ions like silver nitrate (Ag⁺), thallium sulphate (TI⁺), cobalt (II) nitrate (Co²⁺) and arsenic (V) oxide (As⁵⁺) on enzyme activity were researched. Half-maximal inhibitory concentration (IC₅₀) values of Ag⁺, Co²⁺ and As⁵⁺ metal ions, which showed an inhibitory effect, were found to be 0.0044, 0.084 and 4.058 mM, respectively; and their inhibition constants (K _i) were found to be 0.0052 ± 0.00042, 0.087 ± 0.015700 and 4.833 ± 1.753207 mM, respectively. Tl⁺ not exhibited inhibitory effect on the enzyme activity.