Nucleotide monosaccharide intermediates

A large part of the sphingolipids are present as glycolipids. Metabolic Pathway 2, shown below, indicates the known routes of formation of the major nucleotide monosaccharide intermediates i.e. UDPgal, UDPglc, UDPgalNAc and CMPneu-... 

Phosphate esters of glucose, fructose, and other monosaccharides are important metabolic intermediates, and the ribose moiety of nucleotides such as ATP and GTP is phosphorylated at the 5 -position (Figure 7.13). 

UDPG was the first of a whole new class of nucleotides, in which the uridine diphosphate group is attached to a monosaccharide. Two important members of the class are uridine diphosphate glucuronic acid, the intermediate in the synthesis of glucuronides and of many other compounds, and uridine diphosphate N-acetylglucosamine which is an intermediate in the synthesis of mucopolysaccharides. Uridine diphosphate muramic acid was isolated by Park (P2) from Staphylococcus aureus... 

A modification of the monosaccharide units of polysaccharides may obviously be effected at different stages of the biosynthesis of a polymer (a) prior to formation of the activated form of a monosaccharide, (b) at the level of glycosyl nucleotides, (c) at the stage of formation of oligosaccharide intermediates, and (d) after the synthesis of a polymeric chain. 

For rat epiphysial cartilage, the monosaccharide nucleotides and other intermediates (H8) in glycosaminoglycan biosynthesis have been isolated and quantitated. Collation of many of the data on the biosynthetic initiation and propagation of glycosaminoglycan chains has permitted the presentation of an overall scheme (K ), which is given in Section 4.3, p. 30. 

The simple carbohydrates and monosaccharides produced by photosynthetic reactions serve as precursors of more complex molecules produced from them by a variety of biosynthetic pathways. Carbohydrates such as sucrose and the more complex polysaccharide starch are usually considered as direct products of photosynthesis and are synthesised in reactions involving nucleotide sugars as intermediates. 

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