Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
10821793 | Comparative Biochemistry and Physiology Part C: Toxicology & Pharmacology | 2005 | 6 Pages |
Abstract
In vitro and in vivo effects of sublethal ammonia and urea concentrations were assayed on glucose-6-phosphate dehydrogenase (G6PD) of rainbow trout (Oncorhynchus mykiss) erythrocyte. G6PD was purified from erythrocytes with a specific activity of 16.7 EU (mmol NADP+/min)/mg protein and â¼1600-fold in a yield of â¼60% by ammonium sulphate precipitation and 2â²,5â²-ADP Sepharose 4B affinity chromatography. The purity of the enzyme was confirmed using SDS polyacrylamide gel electrophoresis. Experiments with ammonia (2.2-5.5 μM) and urea (20-50 μM) showed the inhibitory effects on the enzyme, in vitro. Inhibition effects were determined in vitro by Lineweaver-Burk and regression graphs. The dissociation constant of the enzyme inhibitor complex (Ki) and 50% inhibitory values were 2.26 ± 1.21 and 2.86 ± 3.51 μM for ammonia and 18.69 ± 6.75 and 23.77 ± 4.58 μM for urea, respectively. In vivo studies in rainbow trout erythrocytes showed significant (p < 0.01) inhibition of G6PD by ammonia and urea. However, ammonia inhibited more than urea since there were significant differences between the final values of erythrocyte G6PD activities.
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Authors
Orhan ErdoÄan, Olcay Hisar, Günay KöroÄlu, Abdulkadir ÃiltaÅ,