Catalyzes the hydroxylation of nicotinate to 6-hydroxynicotinate. Also active against 2-pyrazinecarboxylic acid, but inactive against other nicotinate analogs. H2O + NADP(+) + nicotinate = 6-hydroxynicotinate + H(+) + NADPH Binds 1 Se-Mo-molybdopterin cytosine dinucleotide (Se-Mo-MCD) cofactor per heterotetramer. The cofactor is bound between the NdhL and NdhM subunits. Reversibly inactivated by selenide and sulfide. Not inhibited by cyanide. Most stable at pH 8.0. Unstable at acidic pH values. Cofactor degradation; nicotinate degradation; 6-hydroxynicotinate from nicotinate: step 1/1. Heterooctamer of NDHM, NDHL, NDHS and NDHF. Dimer of heterotetramers. Belongs to the xanthine dehydrogenase family.