A coenzyme C₂₁H₂₇N₇O₁₄P₂ of numerous dehydrogenases that occurs in most cells and plays an important role in all phases of intermediary metabolism as an oxidizing agent or when in the reduced form as a reducing agent for various metabolites.

烟酰胺腺嘌呤二核苷酸辅酶I(多种脱氢酶的一种辅酶，在多数细胞中出现，为中间代谢各阶段的氧化剂，亦为代谢物的还原剂)。