Biochemical studies on the effect of fluoride on higher plants. 2. The effect of fluoride on sucrose-synthesizing enzymes from higher plants

Publisher Website
Google Scholar
Abstract
Phosphoglucomutase (from jack-bean meal), uridine diphosphate glucose pyrophosphorylase and uridine diphosphate glucose-fructose transglucosylase (from dried pea- seed powder), which are involved in sucrose synthesis, were extracted from higher plants, partially purified and characterized with respect to activation by metal ions and inhibition by fluoride. All 3 enzymes required Mg2+ ions for maximum activation but differed in their sensitivity to fluoride. Phosphoglucomutase was inhibited most markedly by fluoride. Uridine diphosphate glucose-fructose transglucosylase was inhibited slightly at higher fluoride concentration, whereas uridine diphosphate glucose pyrophosphorylase was completely insensitive to fluoride. Mn2+ ions gave twice as great an activation of phosphoglucomutase as did Mg2+ ions. The inhibition of phosphoglucomutase by fluoride was proportional to the fluoride concentration, was enhanced by increasing the substrate concentration and was almost independent of the concentration of activating metal ions. Phosphoglucomutase was inhibited sevenfold more by fluoride when Mg2+ ion served as the activator than when Mn2+ ion was activator. Based on the kinetic data, possible mechanisms of the activation by metal ions and the inhibition by fluoride of phosphoglucomutase are examined.