CMAH

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Cytidine monophosphate-N-acetylneuraminic acid hydroxylase (CMP-N-acetylneuraminate monooxygenase)
Identifiers
Symbol(s) CMAH; CSAH
External IDs OMIM: 603209
Orthologs
Human Mouse
Entrez 8418 n/a



Pubmed search [1] n/a

Cytidine monophosphate-N-acetylneuraminic acid hydroxylase (CMP-N-acetylneuraminate monooxygenase), also known as CMAH, is a human gene.[1]

Sialic acids are terminal components of the carbohydrate chains of glycoconjugates involved in ligand-receptor, cell-cell, and cell-pathogen interactions. The two most common forms of sialic acid found in mammalian cells are N-acetylneuraminic acid (Neu5Ac) and its hydroxylated derivative, N-glycolylneuraminic acid (Neu5Gc). Studies of sialic acid distribution show that Neu5Gc is not detectable in normal human tissues although it was an abundant sialic acid in other mammals. Neu5Gc is, in actuality, immunogenic in humans. The absence of Neu5Gc in humans is due to a deletion within the human gene CMAH encoding cytidine monophosphate-N-acetylneuraminic acid hydroxylase, an enzyme responsible for Neu5Gc biosynthesis. Sequences encoding the mouse, pig, and chimpanzee hydroxylase enzymes were obtained by cDNA cloning and found to be highly homologous. However, the homologous human cDNA differs from these cDNAs by a 92-bp deletion in the 5' region. This deletion, corresponding to exon 6 of the mouse hydroxylase gene, causes a frameshift mutation and premature termination of the polypeptide chain in human. It seems unlikely that the truncated human hydroxylase mRNA encodes for an active enzyme explaining why Neu5Gc is undetectable in normal human tissues. Human genomic DNA also shows evidence of this deletion which does not occur in the genomes of African great apes. Nonetheless, the CMAH gene maps to 6p21.32 in humans and great apes indicating that mutation of the CMAH gene occurred following human divergence from chimpanzees and bonobos.[1]

[edit] References

  1. ^ a b Entrez Gene: CMAH cytidine monophosphate-N-acetylneuraminic acid hydroxylase (CMP-N-acetylneuraminate monooxygenase).

[edit] Further reading

  • Varki A (2002). "N-glycolylneuraminic acid deficiency in humans.". Biochimie 83 (7): 615–22. PMID 11522390. 
  • Kawano T, Koyama S, Takematsu H, et al. (1995). "Molecular cloning of cytidine monophospho-N-acetylneuraminic acid hydroxylase. Regulation of species- and tissue-specific expression of N-glycolylneuraminic acid.". J. Biol. Chem. 270 (27): 16458–63. PMID 7608218. 
  • Bonaldo MF, Lennon G, Soares MB (1997). "Normalization and subtraction: two approaches to facilitate gene discovery.". Genome Res. 6 (9): 791–806. PMID 8889548. 
  • Irie A, Koyama S, Kozutsumi Y, et al. (1998). "The molecular basis for the absence of N-glycolylneuraminic acid in humans.". J. Biol. Chem. 273 (25): 15866–71. PMID 9624188. 
  • Irie A, Suzuki A (1998). "CMP-N-Acetylneuraminic acid hydroxylase is exclusively inactive in humans.". Biochem. Biophys. Res. Commun. 248 (2): 330–3. doi:10.1006/bbrc.1998.8946. PMID 9675135. 
  • Chou HH, Takematsu H, Diaz S, et al. (1998). "A mutation in human CMP-sialic acid hydroxylase occurred after the Homo-Pan divergence.". Proc. Natl. Acad. Sci. U.S.A. 95 (20): 11751–6. PMID 9751737. 
  • Muchmore EA, Diaz S, Varki A (1999). "A structural difference between the cell surfaces of humans and the great apes.". Am. J. Phys. Anthropol. 107 (2): 187–98. doi:10.1002/(SICI)1096-8644(199810)107:2<187::AID-AJPA5>3.0.CO;2-S. PMID 9786333. 
  • Hayakawa T, Satta Y, Gagneux P, et al. (2001). "Alu-mediated inactivation of the human CMP- N-acetylneuraminic acid hydroxylase gene.". Proc. Natl. Acad. Sci. U.S.A. 98 (20): 11399–404. doi:10.1073/pnas.191268198. PMID 11562455. 
  • Chou HH, Hayakawa T, Diaz S, et al. (2002). "Inactivation of CMP-N-acetylneuraminic acid hydroxylase occurred prior to brain expansion during human evolution.". Proc. Natl. Acad. Sci. U.S.A. 99 (18): 11736–41. doi:10.1073/pnas.182257399. PMID 12192086. 
  • Strausberg RL, Feingold EA, Grouse LH, et al. (2003). "Generation and initial analysis of more than 15,000 full-length human and mouse cDNA sequences.". Proc. Natl. Acad. Sci. U.S.A. 99 (26): 16899–903. doi:10.1073/pnas.242603899. PMID 12477932. 
  • Mungall AJ, Palmer SA, Sims SK, et al. (2003). "The DNA sequence and analysis of human chromosome 6.". Nature 425 (6960): 805–11. doi:10.1038/nature02055. PMID 14574404. 
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