N-acetyl-D-mannosamine

N-Acetylneuraminic acid aldolase (or sialic acid aldolase, NeuA EC 4.1.3.3) catalyzes the reversible addition of pyruvate (2) to N-acetyl-D-mannosamine (ManNAc (1)) in the degradation of the parent sialic acid (3) (Figure 10.4). The NeuA lyases found in both bacteria and animals are type I enzymes that form a Schiff base/enamine intermediate with pyruvate and promote a si-face attack to the aldehyde carbonyl group with formation of a (4S) configured stereocenter. The enzyme is commercially available and it has a broad pH optimum around 7.5 and useful stability in solution at ambient temperature [36]. 

We propose that the first step in NDP-kasugamine biosynthesis is 2-epimeriza-tion of the postulated UDP-A -acetyl-D-glucosamine precursor, which is suggested by the similarity of the KasQ protein with known UDP-(Af-acetyl-)D-glucosamine 2-epimerases and catalyzes the conversion to UDP-N-acetyl-D-mannosamine. To... 

D-Erythrose-4-phosphate = D-Arabinose-5-phosphate = N -Acetyl-D-mannosamin-6-phosphate... 

N-Acetvlneuraminic Acid Aldolase. A new procedure has also been developed for the synthesis of 9-0-acetyl-N-acetylneuraminic acid using the aldolase catalyzed reaction methodology. This compound is an unusual sialic acid found in a number of tumor cells and influenza virus C glycoproteins (4 ). The aldol acceptor, 6-0-acetyl-D-mannosamine was prepared in 70% isolated yield from isopropenyl acetate and N-acetyl-D-mannosamine catalyzed by protease N from Bacillus subtilis (from Amano). The 6-0-acetyl hexose was previously prepared by a complicated chemical procedure (42.) The target molecule was obtained in 90% yield via the condensation of the 6-0-acetyl sugar and pyruvate catalyzed by NANA aldolase (Figure 6). With similar procedures applied to KDO, 2-deoxy-NANA and 2-deoxy-2-fluoro-NANA were prepared from NANA. 

Synthetic studies for sialic acid and its modifications have extensively used the catabolic enzyme N-acetylneuraminic acid aldolase (NeuA E.C. 4.1.3.3), which catalyzes the reversible addition of pyruvate (70) to N-acetyl-D-mannosamine (ManNAc, 11) to form the parent sialic acid N-acetylneuraminic acid (NeuSNAc, 12 Scheme 2.2.5.23) [1, 2, 45]. In contrast, the N-acetylneuraminic acid synthase (NeuS E.C. 4.1.3.19) has practically been ignored, although it holds considerable synthetic potential in that the enzyme utilizes phosphoenolpyruvate (PEP, 71) as a preformed enol nucleophile from which release of inorganic phosphate during... 

A-Acetyl neuraminic acid aldolase [from Clostridium perfringens, A-acetylneuraminic acid pyruvate lyase] [9027-60-5] [EC 4.1.3.3]. Purified by extraction with H20, protamine pptn, (NH4)2S04 pptn, Me2CO pptn, acid treatment at pH 5.7 and pptn at pH 4.5. The equilibrium constant for pyruvate + n-acetyl-D-mannosamine ++ /V-acetylneuraminidate at 37° is 0.64. The Km for A-acetylneuraminic acid is 3.9mM in phosphate at pH 7.2 and 37°. [Comb and Roseman Methods in Enzymology 5 391 1962). The enzyme from Hogg kidney (cortex) has been purified 1700 fold by extraction with H20, protamine sulphate pptn, (NH4)2S04 pptn, heat treatment between 60-80°, a second (NH4)2S04 pptn and starch gel electrophoresis. The Km for A-acetylneuraminic acid is 1.5mM. [Brunetti et al. JBC 237 2447 1962). 

Scheme 12.—Chemical Synthesis of the Furanose Derivative of N-Acetyl-D-mannosamine.

N-acetylneuraminic acid-like substances. N-acetylneuraminic acid is derived from pyruvic acid and N-acetyl-D-mannosamine. It therefore contains a carboxyl group and a deoxy carbon. It occurs in glycoproteins and complex lipids. 

Figure 17-33. Synthesis of N-acetylneuraminate (Neu5Ac) from N-acetyl-D-glucosamine (GIcNAc) and pyruvate through N-acetyl-D-mannosamine (ManNAc) with N-acetylneuraminate and N-acetyl-D-glucosamine 2-epimerase. Reprinted from Maru et al.I259].

N-Acetyl-D-mannosamine serves as the in situ generated substrate for the synthesis of N-acetylneuraminic acid. Since N-acetyl-D-mannosamine is quite expensive it is synthesized from N-acetyl-D-glucosamine by epimerization at C2. This biotransformation is integrated into the production of N-acetylneuraminic acid (Neu5Ac). 

By application of N-acylglucosamine 2-epimerase it is possible to start with the inexpensive N-acetyl-D-glucosamine instead of N-acetyl-D-mannosamine (Fig. 19-42). The epimerase is used for the in situ synthesis of N-acetyl-D-mannosamine... 

N-acetyl-D-neuraminic acid results from the formation of a C-C bond between the C-1 of N-acetyl-D-mannosamine and the C-3 of phospho-enolpyruvate. This and other derivatives of neuraminic acid are collectively called sialic acids and are widely found in bacteria and animals. 

ROK family (repressor, NanK N-acetyl-D-mannosamine kinase 71, 72... 

S Additional information <1-3, 5, 6, 7, 9> (<1, 3> D-fructose, D-mannose, D-maltose, D-galactose, N-acetyl-D-galactosamine, N-acetyl-D-mannosamine do not serve as substrates [1, 3] <2> N-methyl-D-glucosamine, D-glucosamine, N-acetyl-D-galactosamine, N-acetyl-D-mannosamine do not... 

S ATP + N-acetyl-D-mannosamine (<5> highly specific for ATP and N-acetyl-D-mannosamine [3] <4> metabolic pathway between hexoses and siahc acids [2] <4> enzyme is involved in sialic acid metabolism [5] <4> involved in N-acetylneuraminic acid metabolism, key enzyme in N-acetylneuraminic acid biosynthesis [6,9-11]) (Reversibility [1-12]) [1-12]... 

Rodriguez-Aparicio LB, Ferrero MA, Reglero A. N-acetyl-D-neuraminic acid synthesis in Escherichia coli K1 occurs through condensation of N-acetyl-D-mannosamine and pyruvate. Biochem J 1995 308 501-505. 

Citrate, malate, oxygen at low concentrations (3-5 [xM), proline, succinate N-acetyl-D-glucosamine (GlcNAc), N-acetyl-D-mannosamine, arabinose, arabitol, fructose, glucose, glycerol, maltose, mannitol, mannose, melibiose, ribitol, ribose, sorbitol, sucrose, xylitol... 

Comb, D. G., and S. Roseman Enzymatic synthesis of N-acetyl-D-mannosamine. Biochim. biophys. Acta (Amst.) 29, 653 (1958). 

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