1nur
From Proteopedia
CRYSTAL STRUCTURE OF HUMAN CYTOSOLIC NMN/NaMN ADENYLYLTRANSFERASE
Structural highlights
Function[NMNA3_HUMAN] Catalyzes the formation of NAD(+) from nicotinamide mononucleotide (NMN) and ATP. Can also use the deamidated form; nicotinic acid mononucleotide (NaMN) as substrate with the same efficiency. Can use triazofurin monophosphate (TrMP) as substrate. Can also use GTP and ITP as nucleotide donors. Also catalyzes the reverse reaction, i.e. the pyrophosphorolytic cleavage of NAD(+). For the pyrophosphorolytic activity, can use NAD (+), NADH, NAAD, nicotinic acid adenine dinucleotide phosphate (NHD), nicotinamide guanine dinucleotide (NGD) as substrates. Fails to cleave phosphorylated dinucleotides NADP(+), NADPH and NAADP(+). Protects against axonal degeneration following injury.[1] [2] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedPyridine dinucleotides (NAD and NADP) are ubiquitous cofactors involved in hundreds of redox reactions essential for the energy transduction and metabolism in all living cells. In addition, NAD also serves as a substrate for ADP-ribosylation of a number of nuclear proteins, for silent information regulator 2 (Sir2)-like histone deacetylase that is involved in gene silencing regulation, and for cyclic ADP ribose (cADPR)-dependent Ca(2+) signaling. Pyridine nucleotide adenylyltransferase (PNAT) is an indispensable central enzyme in the NAD biosynthesis pathways catalyzing the condensation of pyridine mononucleotide (NMN or NaMN) with the AMP moiety of ATP to form NAD (or NaAD). Here we report the identification and structural characterization of a novel human PNAT (hsPNAT-3) that is located in the cytoplasm and mitochondria. Its subcellular localization and tissue distribution are distinct from the previously identified human nuclear PNAT-1 and PNAT-2. Detailed structural analysis of PNAT-3 in its apo form and in complex with its substrate(s) or product revealed the catalytic mechanism of the enzyme. The characterization of the cytosolic human PNAT-3 provided compelling evidence that the final steps of NAD biosynthesis pathways may exist in mammalian cytoplasm and mitochondria, potentially contributing to their NAD/NADP pool. Structural characterization of a human cytosolic NMN/NaMN adenylyltransferase and implication in human NAD biosynthesis.,Zhang X, Kurnasov OV, Karthikeyan S, Grishin NV, Osterman AL, Zhang H J Biol Chem. 2003 Apr 11;278(15):13503-11. Epub 2003 Feb 6. PMID:12574164[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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