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In cellular metabolism, NAD is involved in redox reactions, carrying electrons from one reaction to another, so it is found in two forms: NAD + is an oxidizing agent, accepting electrons from other molecules and becoming reduced; with H +, this reaction forms NADH, which can be used as a reducing agent to donate electrons.
These are both forms of NAD — NAD+ is the positively charged form, which has lost an electron, and NADH is the neutral form which has gained an electron, the experts note.
Dehydrogenase enzymes transfer electrons from the substrate to an electron carrier; what carrier is used depends on the reaction taking place. Common electron acceptors used by this subclass are NAD +, FAD, and NADP +. Electron carriers are reduced in this process and considered oxidizers of the substrate.
The NAD+/NADH coenzyme couple act as an electron reservoir for metabolic redox reactions, carrying electrons from one reaction to another. [5] Most of these metabolism reactions occur in the mitochondria. To regenerate NAD+ for further use, NADH pools in the cytosol must be reoxidized.
This energy is supplied by consuming proton motive force to drive electrons in a reverse direction through an electron transport chain and is thus the reverse process as forward electron transport. In some cases, the energy consumed in reverse electron transport is five times greater than energy gained from the forward process. [ 1 ]
An electron transport chain (ETC [1]) is a series of protein complexes and other molecules which transfer electrons from electron donors to electron acceptors via redox reactions (both reduction and oxidation occurring simultaneously) and couples this electron transfer with the transfer of protons (H + ions) across a membrane.
NAD + kinase (EC 2.7.1.23, NADK) is an enzyme that converts nicotinamide adenine dinucleotide (NAD +) into NADP + through phosphorylating the NAD + coenzyme. [6] NADP + is an essential coenzyme that is reduced to NADPH primarily by the pentose phosphate pathway to provide reducing power in biosynthetic processes such as fatty acid biosynthesis and nucleotide synthesis. [7]
The substrates of this enzyme are ATP, deamido-NAD+, L-glutamine, and H 2 O, whereas its 4 products are AMP, diphosphate, NAD +, and glutamate [2] This enzyme participates in glutamate metabolism and nicotinate and nicotinamide metabolism.