Inhibition of Partially Purified Xanthine Oxidase Activity from renal failure patients by Theophylline and Metronidazole

Abstract

Xanthine oxidase (XO) was purified from sera of patients with renal failure by using ammonium sulfate and dialysis with a specific activities 2.1×10-3 and 5.6×10-3 unit/mg protein respectively. By using anion exchange chromatography techniques, One protein peak of XO activity was obtained with specific activity 78×10-3unit/mg protein and with purification fold of 134.02 compared to crude enzyme. One isoenzyme was obtained having a molecular weight of 255344 Dalton approximately.Inhibition of purified XO was studied by deferent concentrations of Theophylline and Metronidazole drugs. The maximal inhibitory effect was exhibited with 70 and 80µM Theophylline and 16 and 18 mM metronidazole. The inhibition type of XO by Theophylline was competitive. Vmax value was 0.0416 unit/ml, and Km value without inhibitor was 0.833 mM, however values were 2 and 2.85 mM, and inhibition constant Ki values were 29.57 and 23.67 mM respectively with 70 and 80µM of Theophylline.The inhibition type of XO by Metronidazole was non competitive. Km value 0.833 mM and Vmax value without inhibitor was 0.0416 unit/ml. However, Vmax values were 0.027 and 0.023 unit/ml and inhibition constant Ki values were 17 and 19mM by using 16 and 18 mM of Metronidazole respectively