nucleoside diphosphate sugars

(NDP-sugars) Compounds formed by the reaction of a phosphorylated hexose sugar with a nucleoside triphosphate (NTP) in the general reaction:
NTP + sugar 1 -phosphate ↔ NDP-sugar + pyrophosphate

ΝDP sugars are important as high-energy glycosyl donors in the synthesis of most polysaccharides, for example the enzyme starch synthase utilizes uridine diphosphate glucose (UDP-glucose) and adenosine diphosphate glucose (ADP-glucose) as substrates. UDP-glucose is the most important of the NDP-sugars. It can be synthesized both from glucose 1-phosphate using the reaction shown above, or from sucrose using the enzyme sucrose synthase (see sucrose ). Besides their importance as glycosyl donors NDP-sugars are important intermediates in the interconversion of monosaccharides and their derivatives. For many enzymes catalysing sugar interconversions, notably the epimerases, NDP-sugars are substrates rather than the sugars themselves or their phosphate esters.