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NNMT
Available structures
PDBOrtholog search: PDBe RCSB
Identifiers
Aliases NNMT, Nnmt, nicotinamide N-methyltransferase
External IDs OMIM: 600008 MGI: 1099443 HomoloGene: 4496 GeneCards: NNMT
Orthologs
SpeciesHumanMouse
Entrez
Ensembl
UniProt
RefSeq (mRNA)

NM_006169

NM_001311062
NM_010924

RefSeq (protein)

NP_006160
NP_001358974
NP_001358975
NP_001358976

NP_001297991
NP_035054

Location (UCSC) Chr 11: 114.26 – 114.31 Mb Chr 9: 48.5 – 48.52 Mb
PubMed search [3] [4]
Wikidata
View/Edit Human View/Edit Mouse

Nicotinamide N-methyltransferase (NNMT) is an enzyme that in humans is encoded by the NNMT gene. [5] NNMT catalyzes the methylation of nicotinamide and similar compounds using the methyl donor S-adenosyl methionine (SAM-e) to produce S-adenosyl-L-homocysteine (SAH) and 1-methylnicotinamide. [6]

Function

Methylation of nicotinamide by NNMT and SAM-e is the major pathway for degradation of nicotinamide leading to excretion in the urine. [6]

Clinical significance

NNMT is highly expressed in the human liver. [6] [7] N-methylation is one method by which drug and other xenobiotic compounds are metabolized by the liver. [6] NNMT expression in adipose tissue is associated with obesity and insulin resistance. [6] [8] Contrary to the negative effects of increased NNMT in adipose tissue, increased NNMT in liver is associated with a better metabolic profile, namely reduced serum triglycerides and free fatty acids. [8] In adipose tissue, NNMT can lead to methylation depletion, whereas because of the many methylation enzymes in the liver NNMT has a negligible effect on liver methylation. [6] But in the liver, the 1-methylnicotinamide produced by NNMT degradation of nicotinamide increases sirtuin 1 (SIRT1) by inhibiting degradation of that protein. [8] Overexpression of SIRT1 in mice has been shown to reduce insulin and fasting glucose, as well as increased metabolism and physical function. [9]

Abundant availability of nicotinamide leads to depletion of both nicotinamide adenine dinucleotide (NAD+) and SAM-e, resulting in liver steatosis and fibrosis, causing the progression from non-alcoholic fatty liver disease (NAFLD) to non-alcoholic steatohepatitis (NASH). [10]

Human embryonic stem cells expression of NNMT is believed to help maintain the cells in a naive state. [6]

NNMT expression is significantly upregulated in many cancers, including pancreatic cancer where levels of NNMT enzyme correlate with increased risk of death. [11] The cause of these correlations has not been established, but may be related to the fact that NNMT enzyme is an inhibitor of DNA repair. [11] NNMT and 1-methylnicotinamide inhibit autophagy in breast cancer, protecting breast cancer cells against oxidative stress. [12] NNMT has been suggested to be a biomarker of cancer. [11]

References

  1. ^ a b c GRCh38: Ensembl release 89: ENSG00000166741Ensembl, May 2017
  2. ^ a b c GRCm38: Ensembl release 89: ENSMUSG00000032271Ensembl, May 2017
  3. ^ "Human PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
  4. ^ "Mouse PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
  5. ^ Aksoy S, Brandriff BF, Ward A, Little PF, Weinshilboum RM (Mar 1996). "Human nicotinamide N-methyltransferase gene: molecular cloning, structural characterization and chromosomal localization". Genomics. 29 (3): 555–61. doi: 10.1006/geno.1995.9966. PMID  8575745.
  6. ^ a b c d e f g Pissios P (2017). "Nicotinamide N-Methyltransferase: More Than a Vitamin B3 Clearance Enzym". Trends in Endocrinology and Metabolism. 28 (5): 340–353. doi: 10.1016/j.tem.2017.02.004. PMC  5446048. PMID  28291578.
  7. ^ Hwang ES, Song SB (2017). "Nicotinamide is an inhibitor of SIRT1 in vitro, but can be a stimulator in cells". Cellular and Molecular Life Sciences. 74 (18): 3347–3362. doi: 10.1007/s00018-017-2527-8. PMID  28417163. S2CID  25896400.
  8. ^ a b c Guarino M, Dufour J (2019). "Nicotinamide and NAFLD: Is There Nothing New Under the Sun?". Metabolites. 9 (9): 180. doi: 10.3390/metabo9090180. PMC  6780119. PMID  31510030.
  9. ^ Bordone L, Cohen D, Robinson A, Motta MC, Guarente L (2007). "SIRT1 transgenic mice show phenotypes resembling calorie restriction". Aging Cell. 6 (6): 759–767. doi: 10.1111/j.1474-9726.2007.00335.x. PMID  17877786. S2CID  16071943.
  10. ^ Komatsu M, Kanda T, Wakino S, Itoh H (2018). "NNMT activation can contribute to the development of fatty liver disease by modulating the NAD + metabolism". Scientific Reports. 8 (1): 8637. Bibcode: 2018NatSR...8.8637K. doi: 10.1038/s41598-018-26882-8. PMC  5988709. PMID  29872122.
  11. ^ a b c Lu XM, Long H (2018). "Nicotinamide N-methyltransferase as a Potential Marker for Cancer". Neoplasma. 65 (5): 656–663. doi: 10.4149/neo_2018_171024N680. PMID  29940773.
  12. ^ Yu H, Zhou X, Wang Y, Zhang J (2018). "Nicotinamide N-methyltransferase inhibits autophagy induced by oxidative stress through suppressing the AMPK pathway in breast cancer cells". Cancer Cell International. 20: 191. doi: 10.1186/s12935-020-01279-8. PMC  7247246. PMID  32489327.

Further reading