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) (PubMed:19002761). Reductase that may be involved in a late step of tobacco alkaloid biosynthesis (PubMed:19002761). Maybe involved in either the formation of a nicotinic acid-derived precursor or the final condensation reaction of tobacco alkaloids (PubMed:19002761). Alkaloid biosynthesis; nicotine biosynthesis. Monomer. Expressed in roots. Induced by methyl jasmonate in roots. Root cells silencing A622L exhibit inhibition of cell growth, severely decreased formation of several alkaloids, and accumulation of nicotinic acid beta-N-glucoside and N-methylpyrrolinium cation. Belongs to the NmrA-type oxidoreductase family. Isoflavone reductase subfamily.