UDP-D- glucose

Phase 2. Recruitment and conversion of an NDP-activated and neutral hex-ose from primary metabolism this is most likely UDP-D-glucose, which by the action of an UDP-glucose 4-epimerase, either the HygJ or HygK protein, respectively, becomes converted into the suggested precursor UDP-D-galactose. 

This enzyme, officially known as l,4-/3-D-xylan synthase [EC 2.4.2.24], catalyzes the reaction of UDP-xylose with (l,4)-)3-D-xylan to yield UDP and (l,4)-/3-D-xylan +i. UDP-D-glucose is also a substrate. 

UDP[U-14C]apiose is extremely labile in the presence of alkali at 4° UDP-D-glucose, on the other hand, was unchanged109 after 18 h at... 

Brummond and Gibbons304 demonstrated the presence, in higher plants, of enzymes that utilize UDP-D-glucose to produce a cellulose-like polymer, and Hassid and coworkers305 separately reported in mung bean a similar enzyme system in which 80-90% of the product consisted of... 

However, other workers claim that UDP-D-glucose may also be an effective donor for cellulose formation with preparations from higher plants, but we could not substantiate their results in our laboratory. 

Subsequently, Ordin and Hall (25, 26) found that particulate preparations from oat coleoptiles could use UDP-D-glucose as substrate for polysaccharide formation. Upon degradation of the polysaccharide derived from UDP-D-glucose with impure cellulase, cellobiose, and to a lesser extent a substance identified as a trisaccharide containing mixed / -(1 - 4), / -(1 - 3) glucosyl linkages were obtained. 

The results indicate that the particulate enzyme contains two enzymes using UDP-D-glucose as substrate, one is capable of synthesizing... 

Xylan. Experiments in vivo by several investigators (30) indicated that xylan in plants originated from glucose by a series of reactions first leading to the formation of pentose polysaccharide. UDP-D-xylose has been isolated from plant seedlings and synthesized enzymically from UDP-D-glucose by the following sequence of reactions ... 

It has been shown that UDP-D-galacturonic acid is present in higher plants (32) and that they contain enzymes which lead to the formation of this uronic acid nucleotide, starting with UDP-D-glucose by the following pathway (33, 34) ... 

Since the discovery of UDP-D-glucose by Leloir,17,18 in 1951, this compound has been implicated in the biosynthesis of a number of D-glucose-containing saccharides.4 It is now well accepted that such gly-cosyl esters are the most important intermediates in the biosynthesis of carbohydrates.1 3,4... 

In the second route, UDP-D-galactose may be synthesized by the action of UTP-a-D-galactosyl phosphate uridyltransferase on UDP-D-glucose and a-D-galactosyl phosphate here, an exchange reaction takes place. 

D-Glucose may be initially phosphorylated by a hexokinase, followed by transformation into a-D-glucosyl phosphate, which is then enzymically converted, in the presence of UTP, into UDP-D-glucose. On the other hand, D-glucose may be converted into UDP-D-galac-... 

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