Pyrophosphate derivatives, donor

During the conversion of anthranilate to tryptophan, two additional carbon atoms must be incorporated to form the indole ring. These are derived from phosphoribosyl pyrophosphate (PRPP) which is formed from ribose 5-phosphate by transfer of a pyro-phospho group from ATP.60 61 The - OH group on the anomeric carbon of the ribose phosphate displaces AMP by attack on Pp of ATP (Eq. 25-5). In many organisms the enzyme that catalyzes this reaction is fused to subunit II of anthranilate synthase.62 PRPP is also the donor of phosphoribosyl groups for biosynthesis of histidine (Fig. 25-13) and of nucleotides (Figs. 

A non-specific bacterial acid phosphatase from Shigella flexneri (PhoN-Sf) has been screened for regioselective phosphorylation of primary alcohol(s) of more than 20 different cyclic and acyclic monosaccharides using pyrophosphate as the phosphate donor (O Scheme 61) [368]. These studies have shown that PhoN-Sf is capable of phosphorylating a range of hexoses (D-glucose epimers, glycosides, and C-2 derivatives), pentoses, heptoses, ketoses, and acyclic carbohydrates. 

The metabolic functions of pantothenic acid in human biochemistry are mediated through the synthesis of CoA. Pantothenic acid is a structural component of CoA. which is necessary for many important metabolic processes. Pantothenic acid is incorporated into CoA by a. series of five enzyme-catalyzed reactions. CoA is involved in the activation of fatty acids before oxidation, which requires ATP to form the respective fatty ocyl-CoA derivatives. Pantothenic acid aI.so participates in fatty acid oxidation in the final step, forming acetyl-CoA. Acetyl-CoA is also formed from pyruvate decarboxylation, in which CoA participates with thiamine pyrophosphate and lipoic acid, two other important coenzymes. Thiamine pyrophosphate is the actual decarboxylating coenzyme that functions with lipoic acid to form acetyidihydrolipoic acid from pyruvate decarboxylation. CoA then accepts the acetyl group from acetyidihydrolipoic acid to form acetyl-CoA. Acetyl-CoA is an acetyl donor in many processes and is the precursor in important biosyntheses (e.g.. those of fatty acids, steroids, porphyrins, and acetylcholine). 

The answer is b. (Murray, pp 627-661. Scriver, pp 3897-3964. Sack, pp 121-138. Wilson, pp 287-320.) Nicotinamide adenine dinucleotide (NAD+) is the functional coenzyme derivative of niacin. It is the major electron acceptor in the oxidation of molecules, generating NADH, which is the major electron donor for reduction reactions. Thiamine (also known as vitamin Bi) occurs functionally as thiamine pyrophosphate and is a coenzyme for enzymes such as pyruvate dehydrogenase. Riboflavin (vitamin B2) functions in the coenzyme forms of flavin mononucleotide (FMN) or flavin adenine dinucleotide (FAD). When concentrated, both have a yellow color due to the riboflavin they contain. Both function as prosthetic groups of oxidation-reduction enzymes or flavoproteins. Flavoproteins are active in selected oxidation reactions and in electron transport, but they do not have the ubiquitous role of NAD+. 

The allyl /i-glycoside of sialyl LacNAc 240 is converted into the sLe derivative by the enzyme-catalyzed transfer of a fucose unit from GDP-fucose to position 3 of the GlcNAc unit under catalysis by -1,3-fucosyltransferase (compare Schemes 37 and 38). The glycosyl donor GDP-fucose may be regenerated by a two-step sequence of enzyme-catalyzed reactions. Under catalysis by pyruvate kinase, spent GDP accepts one phosphate group from enolpyruvate phosphate. The GTP formed reacts with fucose 1-phosphate under catalysis by GDP fucose pyrophosphorylase from porcine thyroid to form GDP-fucose and inorganic pyrophosphate. 

The synthesis of the biosynthetic chitobiosyl donor (46) by a mixed chemical/enzymic process involved attachment of 3,4,6-tri-0-acetyl-2-deoxy-2-acetamido-tt-D-glucose to dolichol via a pyrophosphate bridge by chemical means as shown in Scheme 9. The monosaccharide pyrophosphate (45) then served, after deprotection, in an enzymic formation of the disaccharide (46). Derivatives (47) of 2-deo -2-acetamido>a-D-glucose 1-phosphate were prepared as simple analogues of moenomycin, a complex pentasaccharide which inhibits bacterial cell wall transglycosidation. ... 

The biosynthesis and functions of the membrane glycoproteins of eukaryotic cells have been reviewed. The general features of the biosynthesis of these glycoproteins closely resemble those involved in the biosynthesis of complex bacterial glycans, especially the O-antigen of lipopolysaccharides. Syntheses of polyisoprenyl jS-o-mannopyranosyl phosphate and P -di-A-acetylchitobiosyl P -dolichyl pyrophosphate have been reported. A preparation from human-lymphocyte membranes was able to transfer D-mannose from GPD-o-mannose to the chitobiosyl derivative, whereas dolichyl D-mannosyl phosphate did not act as a D-mannosyl donor. It appears that D-mannosyl residues at various positions of the glycoprotein have different anomeric configurations, so that different D-mannosyl donors are required in their synthesis. 

In the ligation reactions with 3, 5 -diphosphate donors, the T4 RNA ligase shows a strong preference for cytosine (see Table 2.1). However, once the 5 -P mononucleotides or a variety of mononucleotide or nonnucleotide derivatives are adenylylated to form a pyrophosphate-linked product, Ado-5 pp5 -X (AMP-pX), they become effective donor substrates in the presence of acceptors and enzyme, and no longer require the presence of the 3 -P group (13,18). 

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