Catalyzes the formation of NAD(+) from nicotinamide mononucleotide (NMN) and ATP. Involved in the salvage pathway for NAD(+) biosynthesis via NMN (PubMed:24759102). Involved in the filamentation pathway. Suppresses the filamentation defect of a KSS1 deletion (PubMed:21460040). ATP + beta-nicotinamide D-ribonucleotide + H(+) = diphosphate + NAD(+) Optimum pH is 10. Cofactor biosynthesis; NAD(+) biosynthesis; NAD(+) from nicotinamide D-ribonucleotide: step 1/1. Interacts with KSS1 (PubMed:21460040). Interacts with UBC7 (PubMed:22204397). Expression is slightly induced in late log phase. Lowers cellular NAD(+) levels and decreases the efficiency of nicotinamide riboside (NR) utilization, resistance to oxidative stress, and NR-induced life span extension (PubMed:24759102). Highly sensitive to heat shock and higher sensitivity to ER stress agents than wild-type cells (PubMed:22204397). Present with 830 molecules/cell in log phase SD medium. Belongs to the eukaryotic NMN adenylyltransferase family. POF1 subfamily.