Effect of benzimidazole on nicotinamide adenine dinucleotide phosphate phosphomonoesterase activity in wheat leaves.

Nicotinamide adenine dinucleotide phosphate phosphomonoesterase was isolated and partially purified from wheat (Triticum aestivum L. var. Selkirk) leaves. The enzyme had KNADP value of 1.4 X 10(-4) M and a pH optimum of 5.9. In vitro activity of this enzyme was unaffected by precursors of NAD (nicotinamide and nicotinic acid) or cytokinins (kinetin and benzimidazole). However, when detached wheat leaves were treated with solutions of these compounds, the precursors lowered the specific activity while the cytokinins enhanced the activity. It is suggested that spatial separation and compartmentation of the enzyme and its substrate NADP account for the similar effect of benzimidazole on both.