Uridine galactose

Most nucleotide sugars are formed in the cytosol, generally from reactions involving the corresponding nucleoside triphosphate. GMP-sialic acids are formed in the nucleus. Formation of uridine diphosphate galactose (UDP-Gal) requires the following two reactions in mammahan tissues ... 

UDPGal = UDPG Uridine diphosphate galactose 4-epimerase... 

Isselbacher, K. J., A mammalian uridine diphosphate galactose pyrophos-phorylase. J. Biol. Chetn. 232, 429-444 (1958). 

L2. Leloir, L. F., The enzymatic transformation of uridine diphosphate glucose into a galactose derivative. Arch. Biochem. Biophys. 33, 186-190 (1951). 

Uridine diphosphateglucose (UDPGlu), whose structure was confirmed synthetically by Todd (1954), was detected in all organisms surveyed. It was then found to be essential for the utilization of galactose (Leloir, 1950 et seq.) ... 

Seyama, Y., Kalckar, H. M. Specific tritium labeling of uridine diphosphogalactose 4-epimerase by d-1-3H Galactose. Biochemistry 11, 36—39 (1972). 

Wee, T. G., Frey, P. A. Studies on the mechanism of action of uridine diphosphate galactose 4-epimerase. Substate dependent reduction by sodium borohydride. J. Biol. Chem. 248, 33—40 (1973). 

Ketley, J. N., Schellenberg, K. A. Substrate stereochemical requirements in the reductive inactivation of uridine diphosphate galactose 4-epimerase by sugar and 5 -uridine monophosphate. Biochemistry 12, 315—320 (1973). 

B. Galactose and glucose are converted to uridine nucleotides and ultimately inter-... 

UDP-galactose can be converted to UDP-glucose by uridine diphosphogalac-tose 4-epimerase. 

Mild, acidic hydrolysis of the derivative 41 gave uridine 5 -pyrophosphate, 2-acetamido-2-deoxy-D-glucose 6-phosphate, and D-galactose. Alkaline degradation leads to uridine 5 -(2-acetamido-2-deoxy-a-D-glucopyranosyl pyrophosphate) and a-D-galactopyranosyl phosphate, among other products. 

Fermentation procedures useful for the production of uridine 5 -(a-D-galactopyranosyl pyrophosphate) involve the cultivation of bacterial mutant-strains that are deficient in the 4"-epimerase for 30 (see Section V,l,b, p. 369) in D-galactose-containing media,245-247 or by incubating Torulopsis Candida cells with uridine 5 -phosphate, D-galactose, potassium phosphate, and magnesium sulfate.248... 

Experimental conditions have been found for oxidation of uridine 5 -(a-D-galactopyranosyl pyrophosphate) with D-galactose oxidase.265 The reaction product is the a-D-ga(acto-hexodialdose derivative (55). Analogous treatment of uridine 5 -(acetamido-2-deoxy-a-D-galactopy-ranosyl pyrophosphate), and subsequent reduction of the product with sodium borohydride-t, affords a convenient synthesis of the 6 -tritiated derivative.2656... 

It contains the attenuated strain Ty21a of Salmonella typhi. The attenuation is due to the absence of enzyme uridine diphosphate galactose-4-epimerase which is essential for the production of the lipopolysaccharide O antigen. The absence of this enzyme makes Ty21a highly immunogenic. 

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