Nucleoside diphosphate sugar

Nucleoside Diphosphate Sugars.—A polyprenol phosphate containing eleven isoprene units is involved in the biosynthesis of various bacterial cell-wall components.As mentioned in last year s Report, another isoprenoid phosphate, dolichol monophosphate (40), is an intermediate in sugar 

In animal tissues the synthesis of UDPGlc from UTP and glucose-1-phosphate is catalysed by a pyrophosphorylase of widespread occurrence. With the enzyme from human liver, there is no specificity for either the 

Nucleoside Diphosphate Sugars.—The biosynthesis of saccharides from sugar nucleotides has recently been reviewed. The incorporation of monosaccharides into bacterial cell walls involves the participation of 

Vitamin Bg and Related Compounds.—Analogues of pyridoxol and pyridoxal phosphates in which the 5 -methylene (35) or the 5 -phosphate group (36) have been modified have been used to study the substrate specificity of pyridoxine phosphate oxidase. The methylene analogues acted as substrates whereas (36) or the 2-cyanoethyl ester of pyridoxol 

Pyridoxal phosphate is an essential cofactor for many phosphorylases, but whereas pyridoxal phosphate monomethyl ester and the 3 -0-methyl ether bind to apophosphorylase b, the reconstituted enzyme has no activity. Some activation of apophosphorylase b is observed with the A-oxide of pyridoxal phosphate (39), but this appears to be due to a deoxygenation reaction which is catalysed by the enzyme and which produces the pyridoxal phosphate. Apophosphorylase b which had been 

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Other nucleoside diphosphate sugar compounds are known, eg, UDPGal. In addition, the same sugar may be linked to different nucleotides. For example, glucose may be linked to uridine (as shown above) as well as to guanosine, thymidine, adenosine, or cy-tidine nucleotides. 

Synthesis. The synthases are present at the endomembrane system of the cell and have been isolated on membrane fractions prepared from the cells (5,6). The nucleoside diphosphate sugars which are used by the synthases are formed in the cytoplasm, and usually the epimerases and the other enzymes (e.g., dehydrogenases and decarboxylases) which interconvert them are also soluble and probably occur in the cytoplasm (14). Nevertheless some epimerases are membrane bound and this may be important for the regulation of the synthases which use the different epimers in a heteropolysaccharide. This is especially significant because the availability of the donor compounds at the site of the transglycosylases (the synthases) is of obvious importance for control of the synthesis. The synthases are located at the lumen side of the membrane and the nucleoside diphosphate sugars must therefore cross the membrane in order to take part in the reaction. Modulation of this transport mechanism is an obvious point for the control not only for the rate of synthesis but for the type of synthesis which occurs in the particular lumen of the membrane system. Obviously the synthase cannot function unless the donor molecule is transported to its active site and the transporters may only be present at certain regions within the endomembrane system. It has been observed that when intact cells are fed radioactive monosaccharides which will form and label polysaccharides, these cannot always be found at all the membrane sites within the cell where the synthase activities are known to occur (15). A possible reason for this difference may be the selection of precursors by the transport mechanism. 

The important role of glyeosyl esters of nucleoside pyrophosphates (often referred to loosely as sugar nucleotides or nucleoside diphosphate sugars ) in carbohydrate metabolism is well known. Two comprehensive Chapters of this Series,1,2 as well as several surveys in other publications3-5 have already appeared. These reviews deal mainly with the metabolism of these compounds, and... 

Thus, O-glycosyl trichloroacetimidates exhibit in terms of ease of formation, stability, reactivity, and general applicability outstanding glycosyl donor properties they resemble in various aspects the natural nucleoside diphosphate sugar derivatives. Thus, this method has become a very competitive alternative to the existing techniques. 

Glycosyl—Enzyme Complex Intermediates in Biosynthesis of Complex Saccharides. The synthesis of nucleoside diphosphate sugars involves the transfer of a nucleotidyl group from a nucleoside triphosphate to a sugar 1-phosphate with the simultaneous release of pyrophosphate according to the following general reaction (11) ... 

Nucleoside triphosphate + sugar 1-phosphate J pyrophosphorylase nucleoside diphosphate sugar + pyrophosphate... 

Many nucleoside diphosphate sugars containing different bases and different sugar moieties were found to be synthesized by this enzymic process. 

The most abundant structural polysaccharide is plant cellulose, a straight-chain homopolymer of glucose with a /3(1,4) linkage (see chapter 12). Cellulose is formed by the same general mechanism as glycogen, using nucleoside diphosphate sugars. Chitin, a structural polysaccharide found in insects, is also a /3(1,4) homopolymer (fig. 16.3). The... 

E. I. Budowsky, T. N. Druzhinina, G. I. Eliseeva, N. D. Gabrielyan, N. K. Kochetkov, M. A. Novikova, V. N. Shibaev, and G. L. Zhdanov, Synthetic analogues of uridine diphosphate glucose Biochemical and chemical studies. The secondary structure of nucleoside diphosphate sugars, Biochim. Biophys. Acta, 122 (1966) 213-224. 

The metabolic routes leading to polyglucan synthesis were elucidated after the discovery of nucleoside-diphosphate sugars by L. F. Leloir and co-workers in 1955. This finding led to the conclusion that biosynthesis and degradation of glycogen and starch occur by different pathways. 

Nelson, O. E., Chourey, P. S., and Chang, M. T. 1978. Nucleoside diphosphate sugar-starch giucosyl transferase activity in wx starch granules. Plant Physiol 62, 383-386. 

Scheme 41. Chemical strategy for the preparation of nucleoside diphosphate sugars...

Synthesis of glycopyranosylphosphonate analogues of certain natural nucleoside diphosphate sugars as potential inhibitors of gly-cosyltransferases. J. Med. Chem. 1987 30 1383-1391. 42. 

C) they require nucleoside diphosphate sugars for their synthesis... 

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