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 2 [2Fe-2S] clusters per subunit. 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.