title: Inhibition of wheat leaves nitrate reductase activity by cibacron blue.
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.
authors.affiliation: Department of Biochemistry, College of Science, King Saud University, Riyadh, Saudi Arabia.
authors.forename: B A
authors.initials: BA
authors.lastname: Albassam
mesh_terms: D001667:Binding, Competitive; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D020035:Holoenzymes / Q000378:metabolism; D007700:Kinetics; D009243:NAD / Q000378:metabolism; D050901:Nitrate Reductase; D009565:Nitrate Reductases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D009566:Nitrates / Q000378:metabolism; D010269:Paraquat / Q000378:metabolism; D018515:Plant Leaves / Q000201:enzymology; D014227:Triazines / Q000494:pharmacology*; D014908:Triticum / Q000201:enzymology*
chemical_list: D004791:Enzyme Inhibitors; D020035:Holoenzymes; D009566:Nitrates; D014227:Triazines; D009243:NAD; C012842:Cibacron Blue F 3GA; D009565:Nitrate Reductases; D050901:Nitrate Reductase; D010269:Paraquat