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Uridine 5'-diphosphate-glucose dehydrogenase from soybean nodules

Stewart, D.C., Copeland, L.
Plant physiology 1998 v.116 no.1 pp. 349-355
Glycine max, Hordeum vulgare, symbiosis, glucose, developmental stages, root nodules, physicochemical properties, oxidoreductases, Bradyrhizobium japonicum, Triticum aestivum, Brassica napus, kinetics, enzyme activity, protein composition
A highly purified preparation of uridine 5'-diphosphate (UDP)-glucose (Glc) dehydrogenase (DH; EC has been characterized from soybean (Glycine max L.) nodules. The enzyme had native and subunit molecular masses of approximately 272 and 50 kD, respectively. UDP-Glc DH displayed typical hyperbolic substrate kinetics and had Km values for UDP-Glc and NAD+ of 0.05 and 0.12 mM, respectively. Thymidine 5'-diphosphate-Glc and UDP-galactose could replace UDP-Glc as the sugar nucleotide substrate to some extent, but the enzyme had no activity with NADP+. Soybean nodule UDP-Glc DH was labile in the absence of NAD+ and was inhibited by a heat-stable, low-molecular-mass solute in crude extracts of soybean nodules. UDP-Glc DH was also isolated from developing soybean seeds and shoots of 5-d-old wheat and canola seedlings and was shown to have similar affinities for UDP-Glc and NAD+ as those of the soybean nodule enzyme. UDP-Glc DH from all of these sources was most active in young, rapidly growing tissues.