Inorganic pyrophosphatase activity during rice leaf senescence

Abstract

The activities of the acid and alkaline inorganic pyrophosphatases (EC. 3.6.1.1) were determined in attached and detached senescing rice leaves. The acid inorganic pyrophosphatase had the pH optimum at 5.0 and was inhibited by Mg2+, while the alkaline inorganic pyrophosphatase had the pH optimum at 8.6 and had an absolute requirement for Mg2+. The activity of the acid inorganic pyrophosphatase increased, but the activity of the alkaline inorganic pyrophosphatase decreased during senescence of both attached and detached rice leaves. Benzimidazole and kinetin treatment prevented the changes, during senescence, in the activities of both the enzymes. Regression analysis showed strong correlation between chlorophyll, α-amino nitrogen, and acid and alkaline inorganic pyrophosphatase activity during senescence.