Weaning-induced development of delta-opioid receptors in rat brain: differential effects of guanine nucleotides and sodium upon ligand-receptor recognition |
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Authors: | MD Kelly RG Hill A Borsodi G Toth I Kitchen |
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Affiliation: | Department of Biochemistry, College of Science, King Saud University, Riyadh, Saudi Arabia. |
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Abstract: | Cibacron Blue F3GA (CB) inhibited the activities of wheat leaves NADH:nitrate reductase and NADH:cytochrome-c reductase in a time-independent and concentration dependent manner. The methyl viologen:nitrate reductase activity of the enzyme was unaffected by various CB concentrations used in the experiment. Inhibition of NADH:nitrate reductase was of mixed type (partial competitive and pure noncompetitive) with respect to NADH and noncompetitive with respect to nitrate. The estimated inhibition constant (Ki) values were 1 microM for NADH and 8.4 microM for nitrate. The secondary plots of inhibition with respect to NADH, indicated a dissociation constant (KI) of 8.8 microM for the enzyme-NADH-CB complex. This KI being greater than the Ki suggested that the noncompetitive inhibition is predominant over the competitive inhibition at the NADH binding site. |
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