Nicotinamide-nucleotide adenylyltransferase

Humans have three protein isoforms: NMNAT1 (widespread), NMNAT2 (predominantly in brain), and NMNAT3 (highest in liver, heart, skeletal muscle, and erythrocytes). Mutations in the NMNAT1 gene lead to the LCA9 form of Leber congenital amaurosis. Mutations in NMNAT2 or NMNAT3 genes are not known to cause any human disease. NMNAT2 is critical for neurons: loss of NMNAT2 is associated with neurodegeneration. All NMNAT isoforms reportedly decline with age.

Belongs to

This enzyme belongs to the family of transferases, specifically those transferring phosphorus-containing nucleotide groups (nucleotidyltransferases). The systematic name of this enzyme class is ATP:nicotinamide-nucleotide adenylyltransferase. Other names in common use include NAD+ pyrophosphorylase, adenosine triphosphate-nicotinamide mononucleotide transadenylase, ATP:NMN adenylyltransferase, diphosphopyridine nucleotide pyrophosphorylase, nicotinamide adenine dinucleotide pyrophosphorylase, nicotinamide mononucleotide adenylyltransferase, and NMN adenylyltransferase.

Structural studies

As of late 2007, 11 structures have been solved for this class of enzymes, with PDB accession codes 1EJ2, 1GZU, 1HYB, 1KKU, 1KQN, 1KQO, 1KR2, 1M8F, 1M8G, 1M8J, and 1M8K.

Isoform cellular localization

The three protein isoforms have the following cellular localizations

NMNAT1 : Nucleus
NMNAT2 : Cytoplasm
NMNAT3 : Mitochondrion or cytoplasm

All three NMNATs compete for the NMN produced by NAMPT.

Clinical significance

Chronic inflammation due to obesity and other causes reduced NMNAT and NAD+ levels in many tissues.

References

^ Brazill JM, Li C, Zhu Y, Zhai RG (2017). "NMNAT: It's an NAD + Synthase... It's a Chaperone... It's a Neuroprotector". Current Opinion in Genetics & Development. 44: 156–162. doi:10.1016/j.gde.2017.03.014. PMC 5515290. PMID 28445802.
McReynolds MR, Chellappa L, Baur JA (2020). "Age-related NAD + Decline". Experimental Gerontology. 134: 110888. doi:10.1016/j.exger.2020.110888. PMC 7442590. PMID 32097708. S2CID 211237873.
Rajman L, Chwalek K, Sinclair DA (2018). "Therapeutic Potential of NAD-Boosting Molecules: The In Vivo Evidence". Cell Metabolism. 27 (3): 529–547. doi:10.1016/j.cmet.2018.02.011. PMC 6342515. PMID 29514064.
Hurtado-Bagès S, Knobloch G, Ladurner AG, Buschbeck M (2020). "The taming of PARP1 and its impact on NAD + metabolisme". Molecular Metabolism. 38: 100950. doi:10.1016/j.molmet.2020.01.014. PMC 7300387. PMID 32199820.
Yaku K, Okabe K, Nakagawa T (2018). "NAD metabolism: Implications in aging and longevity". Ageing Research Reviews. 47: 1–17. doi:10.1016/j.arr.2018.05.006. PMID 29883761. S2CID 47002665.

ATKINSON MR, JACKSON JF, MORTON RK (1961). "Nicotinamide mononucleotide adenylyltransferase of pig-liver nuclei. The effects of nicotinamide mononucleotide concentration and pH on dinucleotide synthesis". Biochem. J. 80 (2): 318–23. doi:10.1042/bj0800318. PMC 1244001. PMID 13684981.
Dahmen W, Webb B, Preiss J (1967). "The deamido-diphosphopyridine nucleotide and diphosphopyridine nucleotide pyrophosphorylases of Escherichia coli and yeast". Arch. Biochem. Biophys. 120 (2): 440–50. doi:10.1016/0003-9861(67)90262-7. PMID 4291828.
Kornberg A; Pricer WE (1951). "Enzymatic cleavage of diphosphopyridine nucleotide with radioactive pyrophosphate". J. Biol. Chem. 191 (2): 535–541. doi:10.1016/S0021-9258(18)55958-5. PMID 14861199.

Transferases: phosphorus-containing groups (EC 2.7)

2.7.1-2.7.4:
phosphotransferase/kinase
(PO₄)

2.7.1: OH acceptor	Hexo- Gluco- Fructo- Hepatic Galacto- Phosphofructo- 1 Liver Muscle Platelet 2 Riboflavin Shikimate Thymidine ADP-thymidine NAD Glycerol Pantothenate Mevalonate Pyruvate Deoxycytidine PFP Diacylglycerol Phosphoinositide 3 Class I PI 3 Class II PI 3 Sphingosine Glucose-1,6-bisphosphate synthase
2.7.2: COOH acceptor	Phosphoglycerate Aspartate kinase
2.7.3: N acceptor	Creatine
2.7.4: PO₄ acceptor	Phosphomevalonate Adenylate Nucleoside-diphosphate Uridylate Guanylate Thiamine-diphosphate

2.7.6: diphosphotransferase
(P₂O₇)

2.7.7: nucleotidyltransferase
(PO₄-nucleoside)

Polymerase

DNA polymerase

DNA-directed DNA polymerase

I/A

Taq

II/B

Pfu

III/C

IV/X

TDT

V/Y

RNA-directed DNA polymerase

Reverse transcriptase

Telomerase

RNA polymerase

Template-directed

RNA-dependent RNA polymerase

Polyadenylation

PAP

PNPase

Phosphorolytic
3' to 5' exoribonuclease

Nucleotidyltransferase

Guanylyltransferase

mRNA capping enzyme

Other

2.7.8: miscellaneous

Phosphatidyltransferases	CDP-diacylglycerol—glycerol-3-phosphate 3-phosphatidyltransferase CDP-diacylglycerol—serine O-phosphatidyltransferase CDP-diacylglycerol—inositol 3-phosphatidyltransferase CDP-diacylglycerol—choline O-phosphatidyltransferase
Glycosyl-1-phosphotransferase	N-acetylglucosamine-1-phosphate transferase

2.7.10-2.7.13: protein kinase
(PO₄; protein acceptor)

2.7.10: protein-tyrosine	see tyrosine kinases
2.7.11: protein-serine/threonine	see serine/threonine-specific protein kinases
2.7.12: protein-dual-specificity	see serine/threonine-specific protein kinases
2.7.13: protein-histidine	Protein-histidine pros-kinase Protein-histidine tele-kinase Histidine kinase

v t e Enzymes
Activity	Active site Binding site Catalytic triad Oxyanion hole Enzyme promiscuity Diffusion-limited enzyme Cofactor Enzyme catalysis
Regulation	Allosteric regulation Cooperativity Enzyme inhibitor Enzyme activator
Classification	EC number Enzyme superfamily Enzyme family List of enzymes
Kinetics	Enzyme kinetics Eadie–Hofstee diagram Hanes–Woolf plot Lineweaver–Burk plot Michaelis–Menten kinetics
Types	EC1 Oxidoreductases (list) EC2 Transferases (list) EC3 Hydrolases (list) EC4 Lyases (list) EC5 Isomerases (list) EC6 Ligases (list) EC7 Translocases (list)

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