Sugar Nucleotides

Nucleotide sugars are monosaccharides that have a nucleotide, usually uridine triphosphate (UTP), bound to the carbohydrate chain through an energy rich linkage. UTP is synthesized by the de novo pyrimidine biosynthesis. Sugar nucleotides are essential building blocks for metabolism of all living organisms. In plant sugar metabolism, sugar nucleotides are mainly involved in maintenance of carbohydrates. Nucleotide sugars are the activated forms of monosaccharides serving as glycose donors in glycosylation reactions. The sugar nucleotide moiety comprises the sugar derivatives of three of the four ribonucleoside diphosphates and one deoxyribonucle-oside diphosphate, and related compounds. The salvage pathway produces nucleotide sugars by phosphorylation and subsequent pyrophosphorylation of monosaccharides, which are released by cell wall turnover or spontaneous hydrolysis of energy-rich nucleotide sugars in cells. Sugar nucleotides (nucleotide sugars) are the activated forms of nucleotides and sugars. The UDP-glucose plays a key role in plant metabolism.