NADPH-binding protein (PubMed:12369619). Involved in the biosynthesis of pyridine alkaloid natural products, leading mainly to the production of anabasine, anatabine, nicotine and nornicotine, effective deterrents against herbivores with antiparasitic and pesticide properties (neurotoxins); nornicotine serves as the precursor in the synthesis of the carcinogen compound N'-nitrosonornicotine (NNN) (By similarity). Reductase involved in a late step of tobacco alkaloid biosynthesis (By similarity). Triggers either the formation of a nicotinic acid-derived precursor or the final condensation reaction of tobacco alkaloids (By similarity). Alkaloid biosynthesis; nicotine biosynthesis. Monomer. Expressed in roots and stems. In roots, mainly localized in apical zones, including root tips, in both endodermis and cortex tissues (PubMed:12369619). In the differentiated region where root hairs are present, localized in cortex, endodermis and xylem (PubMed:12369619). Stimulated in roots by jasmonic acid (MeJa) in a dose-dependent manner. Belongs to the NmrA-type oxidoreductase family. Isoflavone reductase subfamily.