CMP-N-acetylneuraminic acid

Preuss U, Gu X, Gu T, Yu RK. Purification and characterization of CMP-N-acetylneuraminic acid lactosylceramide (alpha 2-3) sialyltransferase (GM3-synthase) from rat brain. J. Biol. Chem. 1993 268 26273-26278. 

CMP-N-acetylneuraminic acid (CMP-NeuAc). CMP-N-acetylneuraminic acid has been prepared enzymatically on small scales (> 0.5 mmol) from CTP and NeuAc, under catalysis by CMP-NeuAc synthetase (EC 2.7.7.43) [131l An improvement in this procedure, involving in situ production of CTP from CMP under adenylate kinase and pyruvate kinase catalysis, is suitable for multigram-scale synthesis11321. Adenylate kinase catalyzes the equilibration of CTP and CMP to CDP, which is subsequently phosphorylated by pyruvate kinase to provide CTP. A one-pot synthesis of CMP-NeuAc based on this procedure involves the in situ synthesis of NeuAc from N-acetylmannosamine and pyruvate, catalyzed by sialic acid aldolase (Fig. 11.3-12)[10S1. Chemical syntheses of CMP-NeuAc have also been reported11421. 

CMP-N-acetylneuraminic acid synthetase. CMP-NeuNAc synthetase. CMP-sialate pyrophosphorylase. CMP-sialate diphosphorylase. 

A similar example is the biosynthesis of UDP-2-acetamido-2-deoxy-D-glucose and CMP-N-acetylneuraminic acid in rat liver.Here again, both sugars are needed for syntliesis of complex saccharides, and each sugar nucleotide inhibits the first enzyme of the pathway unique to its synthesis, as shown by the dotted arrows in the following Scheme. 

CMP-N-acetylneuraminic acid is formed by a series of reactions which are outgrowths of the pathways of hexosamine biosynthesis. As seen from Fig. 8A, N-acetylmannosamine can be regarded as the first specific intermediate in the biosynthesis of the nucleotide sugar and may be formed by 2-epimerization from either UDP-N-acetylglucosamine or N-acetylglucosamine. The mechanisms of these two reactions have recently been investigated and will be discussed below. 

The continued transformation of IV-acetylmannosamine to CMP-N-acetylneuraminic acid may proceed via either of two routes. As seen from Fig. 8A, IV-acetylneuraminate is an intermediate in the synthesis and may be formed directly from IV-acetylmannosamine and pyruvic acid in a reaction catalyzed by IV-acetylneuraminic acid aldolase or by a series of reactions beginning with the phosphorylation of IV-acetylmannosamine. 

Since none of these enzymes have been extensively purified, they are differentiated from one another primarily by the nature of the acceptor and by the linkage synthesized. TTie general reaction catalyzed by the sialyl-transferases is shown in Fig. 9. Although at least four different sialic acids have been described (Gottschalk, 1960a), only two nucleotide sugar derivatives have been isolated, namely, CMP-2V-acetylneuraminic acid and CMP-N-glycolylneuraminic acid it is presently not known whether different enzymes catalyze the transfer of these two different N-acylneu-raminic acids and most of the sialyltransferase literature is limited to the more readily available CMP-N-acetylneuraminic acid. 

L. Shaw, S. Yousefi, J.W. Dennis and R. Schauer, CMP-N-acetylneuraminic acid hydroxylase activity determines the wheat germ agglutinin-binding phenotype in two mutants of the lymphoma cell line MDAY-D2. Glycoconj. J., 8 (1991) 434-441. 

Carey, D. J., Sommers, L. W., and Hirschberg, C. B., 1980, CMP-N-acetylneuraminic acid Isolation from and penetration into mouse liver microsomes. Cell 19 597-605. 

Kawano, T., Kozutsumi, Y, Kawasaki, T., and Suzuki, A., 1993b, The key enzyme which regulates CMP-N-acetylneuraminic acid hydroxylation is a novel protein, Glycoconj. J. 10 331. 

Kozutsumi, Y, Kawano, T, Kawasaki, H., Suzuki, K., Yamakawa, T, and Suzuki, A., 1991, Reconstitution of CMP-N-acetylneuraminic acid hydroxylation activity using a mouse liver cytosol fraction and soluble cytochrome b5 purified from horse erythrocytes, J. Biochem. 110 429-435. 

Shaw, L., and Schauer, R., 1989, Detection of CMP-N-acetylneuraminic acid hydroxylase activity in fractionated mouse liver, Biochem. J. 263 355-363. 

This particulate enzyme will transfer N-acetylneuraminic acid from CMP-N-acetylneuraminic acid to either exogenously added colominic acid or to endogenous colominic acid found in the particulate preparation. The transfer is apparently to the nonreducing end of the polymer. The enzyme will utilize CMP-N-glycolylneuraminic acid at only 5% the... 

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