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MetaCyc Enzyme: N-acetylneuraminate synthase

Gene: neuB Accession Number: G-10744 (MetaCyc)

Species: Escherichia coli K1

Subunit composition of N-acetylneuraminate synthase = [NeuB]4
         N-acetylneuraminate synthase subunit = NeuB

Summary:
This enzyme has been shown by electrospray mass spectrometry to be a homotetramer, probably composed of two dimers. The primary active form is thought to be tetrameric [Huang05a].

N-acetylneuraminate synthase (sialic acid synthase) participates in the biosynthesis of the α(2-8) poly-N-acetylneuraminate capsular polysaccharide of Escherichia coli K1, a virulence factor for this organism (in [Vann97].

This enzyme is distinguished from the eukaryotic enzyme EC 2.5.1.57 (example N-acetylneuraminate 9-phosphate synthase) which uses N-acetyl-D-mannosamine 6-phosphate as substrate, rather than N-acetyl-β-D-mannosamine.
The apparent molecular mass of the subunit was determined by SDS-PAGE [Vann97].

Gene Citations: [Annunziato95]

Molecular Weight of Polypeptide: 38.694 kD (from nucleotide sequence), 40.0 kD (experimental) [Vann97 ]

Unification Links: DIP:DIP-28128N , Protein Model Portal:Q46675 , UniProt:Q46675

Relationship Links: Entrez-Nucleotide:PART-OF:U05248 , InterPro:IN-FAMILY:IPR006190 , InterPro:IN-FAMILY:IPR013132 , InterPro:IN-FAMILY:IPR013785 , InterPro:IN-FAMILY:IPR013974 , InterPro:IN-FAMILY:IPR020007 , Pfam:IN-FAMILY:PF03102 , Pfam:IN-FAMILY:PF08666 , Prosite:IN-FAMILY:PS50844 , Smart:IN-FAMILY:SM00858

Gene-Reaction Schematic: ?

Credits:
Created 03-Jul-2008 by Fulcher CA , SRI International


Enzymatic reaction of: N-acetylneuraminate synthase

Synonyms: sialic acid synthase, N-acetylneuraminic acid synthase, N-acetylneuraminic acid synthetase, NeuAc synthase, sialate synthase

EC Number: 2.5.1.56

phosphoenolpyruvate + N-acetyl-D-mannosamine + H2O <=> N-acetyl-β-neuraminate + phosphate

The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the Enzyme Commission system.

The reaction is favored in the direction shown.

In Pathways: superpathway of sialic acids and CMP-sialic acids biosynthesis , CMP-N-acetylneuraminate biosynthesis II (bacteria)

Summary:
This enzyme catalyzes the condensation of N-acetyl-β-D-mannosamine with phosphoenolpyruvate, producing N-acetylneuraminate and phosphate (reviewed in [Tanner05]. The enzyme showed a high degree of substrate specificity [Vann97, Komaki97].

Inhibitors (Unknown Mechanism): Hg2+ [Komaki97] , Ag+ [Komaki97] , Cu2+ [Komaki97] , N-bromosuccinimide [Komaki97] , semicarbazide [Komaki97] , p-chloromercuribenzoate [Komaki97] , hydroxylamine [Komaki97] , I2 [Komaki97]

Kinetic Parameters:

Substrate
Km (μM)
Citations
phosphoenolpyruvate
40.0
[Komaki97]
N-acetyl-D-mannosamine
5600.0
[Komaki97]

T(opt): 35 °C [Komaki97]

pH(opt): 7.5 [Komaki97]


References

Angata02: Angata T, Varki A (2002). "Chemical diversity in the sialic acids and related alpha-keto acids: an evolutionary perspective." Chem Rev 102(2);439-69. PMID: 11841250

Annunziato95: Annunziato PW, Wright LF, Vann WF, Silver RP (1995). "Nucleotide sequence and genetic analysis of the neuD and neuB genes in region 2 of the polysialic acid gene cluster of Escherichia coli K1." J Bacteriol 177(2);312-9. PMID: 7814319

Cox02a: Cox AD, Hood DW, Martin A, Makepeace KM, Deadman ME, Li J, Brisson JR, Moxon ER, Richards JC (2002). "Identification and structural characterization of a sialylated lacto-N-neotetraose structure in the lipopolysaccharide of Haemophilus influenzae." Eur J Biochem 269(16);4009-19. PMID: 12180977

Hood99: Hood DW, Makepeace K, Deadman ME, Rest RF, Thibault P, Martin A, Richards JC, Moxon ER (1999). "Sialic acid in the lipopolysaccharide of Haemophilus influenzae: strain distribution, influence on serum resistance and structural characterization." Mol Microbiol 33(4);679-92. PMID: 10447878

Huang05a: Huang HH, Liao HK, Chen YJ, Hwang TS, Lin YH, Lin CH (2005). "Structural characterization of sialic acid synthase by electrospray mass spectrometry--a tetrameric enzyme composed of dimeric dimers." J Am Soc Mass Spectrom 16(3);324-32. PMID: 15734325

Komaki97: Komaki E, Ohta Y, Tsukada Y (1997). "Purification and characterization of N-acetylneuraminate synthase from Escherichia coli K1-M12." Biosci Biotechnol Biochem 61(12);2046-50. PMID: 9438985

Severi05: Severi E, Randle G, Kivlin P, Whitfield K, Young R, Moxon R, Kelly D, Hood D, Thomas GH (2005). "Sialic acid transport in Haemophilus influenzae is essential for lipopolysaccharide sialylation and serum resistance and is dependent on a novel tripartite ATP-independent periplasmic transporter." Mol Microbiol 58(4);1173-85. PMID: 16262798

Severi08: Severi E, Muller A, Potts JR, Leech A, Williamson D, Wilson KS, Thomas GH (2008). "Sialic acid mutarotation is catalysed by the Escherichia coli beta -propeller protein YJHT." J Biol Chem 283(8):4841-9. PMID: 18063573

Tanner05: Tanner ME (2005). "The enzymes of sialic acid biosynthesis." Bioorg Chem 33(3);216-28. PMID: 15888312

Vann97: Vann WF, Tavarez JJ, Crowley J, Vimr E, Silver RP (1997). "Purification and characterization of the Escherichia coli K1 neuB gene product N-acetylneuraminic acid synthetase." Glycobiology 7(5);697-701. PMID: 9254051


Report Errors or Provide Feedback
Please cite the following article in publications resulting from the use of MetaCyc: Caspi et al, Nucleic Acids Research 42:D459-D471 2014
Page generated by SRI International Pathway Tools version 18.5 on Fri Nov 28, 2014, biocyc13.