Phenolic acids inhibited the activities of wheat leaf nitrate reductase depending on phenolic structure and concentration. Possible conformational change(s) in the enzyme induced by hydrogen bonding and/or hydrophobic interactions might be the cause of the enzyme inhibition. NADH:cytochrome C reductase partial activity was unaffected, which indicates that terminal nitrate-reducing domain of NR may be the site of polyphenol binding.
