Catalyzes the deamidation of nicotinamide, an early step in the NAD(+) salvage pathway. Prevents the accumulation of intracellular nicotinamide, a known inhibitor of poly(ADP-ribose) polymerases (PARP enzymes). May play a role in the regulation of seed germination potential. H2O + nicotinamide = NH4(+) + nicotinate Cofactor biosynthesis; nicotinate biosynthesis; nicotinate from nicotinamide: step 1/1. Expressed during seed germination. Delayed seed germination, reduced seed germination potential and increased sensitivity to abscisic acid (ABA) during germination. Belongs to the isochorismatase family.