NADPH, the reduced from of nicotinamide adenine dinucleotide phosphate, serves as a major reducing agent in biological systems. The oxided form is abbreviated as NADP+. NADPH is a hydride ion donor. Although NADPH and NADH differ by only the presence of the 2'-phosphate group in NADPH (bottome of structure), their chemistries are drastically different. It is generated by the malate enzyme, photosystems, and in the pentose phosphate pathway.