This is the nuclear NMNAT isoform. It catalyzes the formation of NAD+ from nicotinamide mononucleotide (NMN) and ATP. It can also use the deamidated form of nicotinic acid mononucleotide (NAMN) as substrate with the same efficiency. It interacts with PARP-1/ARTD1. It protects against axonal degeneration following mechanical or toxic insults. It is widely expressed.