Nucleoside sugar phosphates, synthesis

Both chemical and enzymatic syntheses have been reported of nucleoside sugar phosphates.88 An enzymatic synthesis of UDP-d-G1cNAc is shown next 95... 

The sugar configuration about the T, 2, 3, and 4 positions can be changed by synthesis. A variety of pyrimidine nucleoside cyclic phosphates have been made. Ukita et al. (425) prepared -D-lyxo-uridine 2 3 -cyclic phosphate (Fig. 21a). The configuration about the 2 and 3 positions is inverted and the two OH groups are now cis to the base rather than trans as in the D-ribose series. No hydrolysis at all of this compound was observed in the presence of RNase. However, both the cyclic phosphate and the free 2 (3 )-nucleotides inhibit the enzyme. The... 

Synthesis.—Comprehensive reviews on glycosyl esters of nucleoside pyrc>-phosphates and teichoic acids have appeared in the past year as have details of the preparation of xylulose-5-phosphate using transketolase. Phosphorylation of glucose by inorganic phosphate in the presence of histidine occurs under simulated primitive earth conditions and the reactive species is probably an iST-phosphorylated histidine. Phosphorylation of sugars by heating them with 100% phosphoric acid in vacuo is a novel experimental... 

The approach described in this Section involves the use of suitably protected, phosphorylated sugars as starting materials. These sugar phosphates are then converted into nucleotides by methods - previously employed in the synthesis of nucleosides. In general, these approaches... 

Thymidine phosphorylase occurs in most microorganisms however, its absence from lactobacilli is noteworthy (4). The E. coli enzyme has been partly purified 9-11) and will phosphorolyze deoxyuridine derivatives with various substituents at the pyrimidine 5-position, but will not accept those with a 4-amino group. Thymidine phosphorylase is quantitatively released from E. coli cells by osmotic shock, a result which is thought to mean that the enzyme is located near the cell surface 21). When wild-type E. coli cells are provided with thymidine, initially the deoxyribo-nucleoside is utilized for DNA synthesis. However, this soon ceases because the synthesis of thymidine phosphorylase is induced and, as a result, thymidine is cleaved to the free base and the sugar phosphate degraded. 

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) ... 

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