Monovalent-stimulated adenosine triphosphatase as influenced by nitrate reductase in wheat roots

Adenosine triphosphatase (ATPase) was isolated and studied in cell free preparation from 10 days old wheat roots. The enzyme showed single peak at acidic pH of 6.0. Monovalent ions, Na⁺ and K⁺, when included in the assay medium, significantly stimulated the activity of the enzyme (47% – 54%), stimulation with K⁺was slightly more than that with Na⁺. When taken alone, Mg²⁺ ions did not stimulate the enzyme activity but interestingly registered a marginal decrease. Further inclusion of Na⁺ and K⁺ along with Mg²⁺, however, brought the enzyme activity near to the basal level. NO⁻₃ and Cl⁻ tested did not influence the activity of the enzyme. After placing the whole wheat plants, with roots dipped in nitrate solution (contained in darkened beaker), in light for 4 hr, nitrate reductase (NR) and (Na⁺ – K⁺) - stimulated ATPase were determined in cell free preparation. The activity of former increased significantly (45%), while latter exhibited inhibition (49%). Influence of NR on the level of Na⁺ and K⁺ - stimulated ATPase activity is discussed.