Purification and kinetics of sheep kidney cortex glucose-6-phosphate dehydrogenase

Glucose-6-phosphate dehydrogenase (G-6-PD) is one of the important enzymes, which is responsible for the production of NADPH and ribose-5-phosphate. NADPH is used for the biosynthetic reactions and protection of the cells from free radicals. We have investigated some properties and kinetic mechanism of the sheep kidney cortex G-6-PD. This enzyme has been purified 1384-fold with a yield of 16.96% and had a specific activity of 27.69 U/mg protein. The purification procedure consists of 2′, 5′-ADP-Sepharose 4B affinity chromatography after ultracentrifugation. The sheep kidney cortex G-6-PD was found to operate according to a Ping Pong Bi Bi mechanism. The kinetic parameters from sheep Km values for G-6-P and NADP+ and Vm were determined to be 0.041 ± 0.0043 mM, 0.0147 ± 0.001 mM and 28.23 ± 0.86 μMol min− 1 mg protein− 1, respectively. The pH optimum was 7.4 and the optimum temperature was 45 °C. In our previous study we have found that lamb kidney cortex G-6-PD enzyme obeys ‘Ordered Bi Bi’ mechanism. We suggest that kinetic mechanism altered due to the aging since sheep G-6-PD uses a ‘ping pong’ mechanism.