Background：Catalyzes the formation of NAD(+) from nicotinamide mononucleotide(NMN) and ATP(PubMed:17402747). Can also use the deamidated form; nicotinic acid mononucleotide(NaMN) as substrate with the same efficiency(PubMed:17402747). Can use triazofurin monophosphate(TrMP) as substrate(PubMed:17402747). Also catalyzes the reverse reaction, i.e. the pyrophosphorolytic cleavage of NAD(+)(PubMed:17402747). For the pyrophosphorolytic activity, prefers NAD(+) and NaAD as substrates and degrades NADH, nicotinic acid adenine dinucleotide phosphate(NHD) and nicotinamide guanine dinucleotide(NGD) less effectively(PubMed:17402747). Involved in the synthesis of ATP in the nucleus, together with PARP1, PARG and NUDT5(PubMed:27257257). Nuclear ATP generation is required for extensive chromatin remodeling events that are energy-consuming(PubMed:27257257). Fails to cleave phosphorylated dinucleotides NADP(+), NADPH and NaADP(+)(PubMed:17402747). Protects against axonal degeneration following mechanical or toxic insults(By similarity).
