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In general, NADP + is synthesized before NADPH is. Such a reaction usually starts with NAD + from either the de-novo or the salvage pathway, with NAD + kinase adding the extra phosphate group. ADP-ribosyl cyclase allows for synthesis from nicotinamide in the salvage pathway, and NADP + phosphatase can convert NADPH back to NADH to maintain a ...
In contrast, the main function of NADPH is as a reducing agent in anabolism, with this coenzyme being involved in pathways such as fatty acid synthesis and photosynthesis. Since NADPH is needed to drive redox reactions as a strong reducing agent, the NADP + /NADPH ratio is kept very low. [62]
The source of the NADPH is two-fold. When malate is oxidatively decarboxylated by "NADP +-linked malic enzyme" to form pyruvate, CO 2 and NADPH are formed. NADPH is also formed by the pentose phosphate pathway which converts glucose into ribose, which can be used in synthesis of nucleotides and nucleic acids, or it can be catabolized to ...
The pentose phosphate pathway. The pentose phosphate pathway (also called the phosphogluconate pathway and the hexose monophosphate shunt or HMP shunt) is a metabolic pathway parallel to glycolysis. [1] It generates NADPH and pentoses (five-carbon sugars) as well as ribose 5-phosphate, a precursor for the synthesis of nucleotides. [1]
The chemical pathway of oxygenic photosynthesis fixes carbon in two stages: the light-dependent reactions and the light-independent reactions. The light-dependent reactions capture light energy to transfer electrons from water and convert NADP + , ADP , and inorganic phosphate into the energy-storage molecules NADPH and ATP .
The main carboxylating enzyme in C 3 photosynthesis is called RuBisCO, which catalyses two distinct reactions using either CO 2 (carboxylation) or oxygen (oxygenation) as a substrate. RuBisCO oxygenation gives rise to phosphoglycolate , which is toxic and requires the expenditure of energy to recycle through photorespiration .
Ferredoxin: NADP + reductase is the last enzyme in the transfer of electrons during photosynthesis from photosystem I to NADPH. [2] The NADPH is then used as a reducing equivalent in the reactions of the Calvin cycle. [2] Electron cycling from ferredoxin to NADPH only occurs in the light in part because FNR activity is inhibited in the dark. [11]
The gluconeogenesis pathway is highly endergonic until it is coupled to the hydrolysis of ATP or guanosine triphosphate (GTP), effectively making the process exergonic. For example, the pathway leading from pyruvate to glucose-6-phosphate requires 4 molecules of ATP and 2 molecules of GTP to proceed spontaneously.