Uridine diphosphoglucose pyrophosphorylase of pea seeds

Abstract

Uridine diphosphoglucose pyrophosphorylase, which catalyzes the reaction uridine diphosphoglucose + inorganic pyrophosphate [image] uridine triphosphate + glucose 1-phosphate was found in pea-seed extracts. A purified preparation free from interfering enzymes was obtained. The apparent equilibrium of the reaction was in favor of uridine triphosphate formation. The apparent equilibrium constant (uridine triphosphate) (glucose 1-phosphate)/(uridine diphosphoglucose) (inorganic pyrophosphate)) was affected by Mg2+ ion concentration and pH. Mg2+ ions, which could be replaced by Mn2+, Co2+ or Ni2+ ions, were essential for the reaction. The effects of Mg2+ ion concentration, concentration of substrates, pH and inhibitors on the pyrophosphorolysis of uridine diphosphoglucose were studied. Active preparations of the enzyme were obtained from a number of plant tissues. The possible relationship of the reaction catalyzed by the enzyme to the carbohydrate metabolism of plants is discussed.