Biosynthesis of Insoluble Glucans From Uridine-Diphosphate-d-Glucose With Enzyme Preparations From Phaseolus aureus and Lupinus albus

Particulate, and digitonin-solubilized, enzyme systems from Phaseolus aureus and Lupinus albus catalyze the biosynthesis of aqueous-insoluble glucans from UDP-d-glucose. The digitonin treatment greatly increases the enzymic activity of (per unit protein) both the 34,000g pellet and the supernatant liquid as compared with that of the original particles. Most of the polymer produced (90-95%) is soluble in hot, dilute alkali; the interglucosidic linkages of the alkali-soluble and alkali-insoluble polymers are identical. The optimum concentration for the incorporation of radioactivity from UDP-d-glucose-(14)C into soluble glucan is high; at 10(-3)m at least 50% of the added radioactive glucosyl donor is incorporated.Careful examination of the products of degradation of the polymers produced by various enzymic preparations showed that beta-(1-->3)-glucans are produced. No evidence was obtained for any measurable amount of beta-(1-->4)-d-glucose linkages.