Aquacobalamin reductase (NADPH) (EC 126.96.36.199) is an enzyme that catalyzes the chemical reaction
2 cob(II)alamin + NADP+
2 aquacob(III)alamin + NADPH + H+
Thus, the two substrates of this enzyme are cob(II)alamin and nicotinamide adenine dinucleotide phosphate ion, whereas its 3 products are aquacob(III)alamin, nicotinamide adenine dinucleotide phosphate, and hydrogen ion.
This enzyme belongs to the family of oxidoreductases, specifically those oxidizing metal ion with NAD+ or NADP+ as acceptor. The systematic name of this enzyme class is cob(II)alamin:NADP+ oxidoreductase. Other names in common use include aquacobalamin (reduced nicotinamide adenine dinucleotide phosphate), reductase, NADPH-linked aquacobalamin reductase, and NADPH2:aquacob(III)alamin oxidoreductase. This enzyme participates in porphyrin and chlorophyll metabolism. It employs one cofactor, FAD.