NAD+ is one of those subjects where the details matter more than the headlines. This page pulls together the background, the mechanisms, and the practical points readers ask about most.
Updated 2025-10-30. Numbers and descriptions here follow the published literature rather than marketing material.
In humans, NAD+ can be synthesized from nicotinic acid, nicotinamide, nicotinamide riboside, and tryptophan through overlapping pathways. The salvage pathway recycles nicotinamide back to NAD+ and is often considered a major route in many tissues. Dietary precursors and intracellular recycling both contribute to the pool, but the quantitative importance of each source remains an active research question. NAD+ levels are not uniform across organs or cell compartments. Measurements in blood do not necessarily reflect concentrations inside tissues.
NAD+ is a dinucleotide composed of nicotinamide, ribose, and adenine linked by phosphate groups. Its full name is nicotinamide adenine dinucleotide, with "+" denoting the oxidized form. The molecule acts as a coenzyme in redox reactions, cycling between NAD+ and NADH. In cells, it participates in electron transfer during glycolysis, the citric acid cycle, and oxidative phosphorylation. It is distinct from NADP+, which carries an additional phosphate group and supports different biosynthetic reactions.
Cells produce NAD+ through several biosynthetic routes. The salvage pathway recycles nicotinamide, while the Preiss-Handler pathway uses nicotinic acid, and a de novo route can start from tryptophan in some organisms. In mammals, the salvage pathway is generally considered the main source under ordinary conditions. Tissue concentrations vary widely by cell type and compartment, and measured declines with age have been reported in some studies. Whether such changes drive aging or mainly accompany it remains an open question.
Nicotinamide adenine dinucleotide, commonly abbreviated NAD+, is a coenzyme present in all living cells. The molecule consists of two nucleotides linked by phosphate groups, with adenine and a nicotinamide ring as its principal features. In its oxidized form, the nicotinamide ring can accept a hydride ion, becoming NADH. This reversible conversion places NAD+ at the center of many electron-transfer reactions. Its role as a redox carrier is well established across bacteria, plants, fungi, and animals.
Beyond redox chemistry, NAD+ acts as a substrate for several enzyme families. ADP-ribosyltransferases, sirtuins, and CD38 ectoenzymes cleave the molecule into nicotinamide and ADP-ribose or related products. These reactions connect NAD+ availability to processes such as DNA repair, chromatin modification, and calcium signaling. Because the coenzyme is used in both electron transfer and signaling, cells maintain separate pools in compartments including the cytosol, mitochondria, and nucleus. The relative sizes and regulation of those pools remain active areas of study.
| Property | Value | Notes |
|---|---|---|
| Common name | Nicotinamide adenine dinucleotide (oxidized) | Often shortened to NAD+ |
| Chemical class | Dinucleotide | Contains nicotinamide and adenine moieties |
| Molecular formula | C21H27N7O14P2 | Free acid form; charge depends on pH |
| Molar mass | About 663.43 g/mol | Calculated for C21H27N7O14P2 |
| CAS number | 53-84-9 | Common identifier for beta-NAD+ |
Quality control for NAD+ materials typically combines identity, purity, and water content checks. Identity may be confirmed by ultraviolet spectrum, retention time in chromatography, or mass accuracy, while purity is assessed by HPLC peak area or quantitative nuclear magnetic resonance. Residual water and solvents can affect molar calculations and enzyme assays, so Karl Fischer titration or thermogravimetric analysis may be used. Commercial materials vary in grade and counterion form, and published methods should specify the exact salt or hydrate when reporting concentrations. Regulatory status depends on intended use, with research reagents, dietary ingredients, and clinical products treated under different frameworks.
Quantification of NAD+ in biological samples usually relies on separation techniques coupled to sensitive detection. High-performance liquid chromatography with ultraviolet detection can measure the oxidized form by its absorbance near 260 nm, while mass spectrometry provides greater specificity and can distinguish NAD+ from close analogs. Enzymatic cycling assays use coupled dehydrogenase reactions to amplify signal and estimate NAD+ concentrations in cell or tissue extracts. Because NAD+ and NADH interconvert rapidly, sample preparation must quench metabolism quickly and preserve the redox state before analysis.
The stability of NAD+ depends on pH, temperature, light exposure, and the presence of degradative enzymes. Aqueous solutions are generally more stable under mildly acidic to neutral conditions and degrade faster under alkaline conditions or prolonged heat. The solid is hygroscopic and should be stored desiccated, often frozen, and protected from repeated freeze-thaw cycles. In laboratory handling, aliquots reduce repeated temperature changes, and chelating agents may limit metal-catalyzed hydrolysis in some buffers. These practices matter because even small amounts of NADH or hydrolysis products can interfere with quantitative assays.
In glycolysis, NAD+ accepts electrons during the oxidation of glyceraldehyde-3-phosphate, forming NADH. The tricarboxylic acid cycle and fatty acid oxidation also generate NADH, which donates electrons to the mitochondrial electron transport chain. This flow supports ATP synthesis and helps maintain the redox balance of the cell. Other dehydrogenases use NAD+ as a cofactor for biosynthetic reductions and detoxification reactions. NADH is later reoxidized to sustain continued flux through these pathways.
Beyond electron transfer, NAD+ serves as a substrate for enzymes that cleave the molecule and transfer ADP-ribose units. Sirtuins, poly(ADP-ribose) polymerases, and CD38 consume NAD+ in regulatory reactions. These activities link NAD+ availability to DNA repair, chromatin modification, calcium signaling, and metabolic stress responses. Because consumption can exceed biosynthesis under some conditions, cellular NAD+ levels are dynamic rather than fixed. Enzyme affinity and local synthesis also influence how much NAD+ is available for signaling.
NAD+ is a dinucleotide composed of adenine, ribose, and nicotinamide moieties linked by phosphate groups. Its oxidized form carries a positive charge on the nicotinamide ring, which enables reversible hydride transfer. The molecule functions as a coenzyme in oxidoreductase reactions rather than as a dietary vitamin in its intact form. Cells maintain separate pools in cytoplasm, mitochondria, and nucleus. This compartmentalization allows distinct redox environments while preserving a shared chemical identity.
Related compounds include NADH, the reduced form, and NADP+, which carries an additional phosphate group. NADP+ and NADPH often serve in biosynthetic and antioxidant reactions, while NAD+ and NADH are more associated with energy-yielding catabolism. Nicotinamide, nicotinic acid, and nicotinamide riboside are precursors that can enter salvage pathways. The exact contribution of dietary precursors to tissue NAD+ pools is an area of active investigation. Some studies measure labeled precursors to trace those routes.
NAD+ is the oxidized form of nicotinamide adenine dinucleotide, a coenzyme built from two nucleotides joined by a phosphate linkage. One nucleotide carries adenine, and the other carries nicotinamide; the plus sign denotes a formal positive charge on the nicotinamide ring, not a free proton. In cells, NAD+ and its reduced partner NADH form a reversible redox pair. That pair participates in electron transfer reactions throughout metabolism. The abbreviation NAD+ is common in biochemistry, while NAD(H) sometimes denotes the combined pool.
This tornado was part of a small outbreak that affected Europe that day, which produced a total of seven tornadoes. In Poland, one person was injured by an F2 tornado that impacted the towns of Librantowa and Koniuszowa, damaging numerous structures, 15 of which had their roofs torn off. Numerous reports of damaging straight-line winds and large, destructive hail were received as well. Weather of 2021 List of tornadoes rated on the International Fujita scale List of European tornadoes and tornado outbreaks List of F4 and EF4 tornadoes List of F4 and EF4 tornadoes (2020–present) October 2022 European tornado outbreak – An EF3 tornado struck Bihucourt F4 Tornado Hits Hodonín, Czechia - Jun. 24, 2021 tornádo v Hodoníně F4 Tornado Hits Hodonín, Czechia - Jun. 24, 2021 tornádo v Hodoníně (Part 2) Inside of an F4 tornado (full version)
The DLD homodimer functions as the E3 component of the pyruvate, α-ketoglutarate, α-adipate and branched-chain amino acid-dehydrogenase complexes and the glycine cleavage system, all in the mitochondrial matrix. In these complexes, DLD converts dihydrolipoic acid and NAD+ into lipoic acid and NADH. DLD also has diaphorase activity, being able to catalyze the oxidation of NADH to NAD+ by using different electron acceptors such as O2, labile ferric iron, nitric oxide, and ubiquinone. DLD is thought to have a pro-oxidant role by reducing oxygen to a superoxide or ferric to ferrous iron, which then catalyzes production of hydroxyl radicals. Diaphorase activity of DLD may have an antioxidant role through its ability to scavenge nitric oxide and to reduce ubiquinone to ubiquinol. The dihyrolipamide dehydrogenase gene is known to have multiple splice variants.
5-Hydroxyeicosanoid dehydrogenase (5-HEDH) or more formally, nicotinamide adenine dinucleotide phosphate (NADP+)-dependent dehydrogenase, is an enzyme that metabolizes between two eicosanoid metabolites of arachidonate 5-lipoxygenase (5-LOX): 5-hydroxyeicosatetraenoic acid (5-(S)-HETE), and its 5-keto analog 5-oxo-eicosatetraenoic acid (5-oxo-ETE). It also acts in the reverse direction, metabolizing 5-oxo-ETE to 5(S)-HETE. Since 5-oxo-ETE is 30–100-fold more potent than 5(S)-HETE in stimulating various cell types, 5-HEDH is regarded as a regulator and promoter of the influence that 5-LOX and its metabolites have on cell function. Although 5-HEDH has been evaluated in a wide range of intact cells and in crude microsome preparations, it has not yet been evaluated for its structure or gene, and most studies on it have been limited to human tissues.
July 28 – August 4: 2018 Senior League Baseball World Series in Easley at Easley Recreation Complex The Pariba Little League (Caribbean) defeated the Naamans Little League (East), 7–2, in the final. July 29 – August 5: 2018 Little League Intermediate (50/70) Baseball World Series in Livermore at Max Baer Park The West Seoul LL (Asia-Pacific) defeated the Livermore/Granada LL (Host), 10–0, in the final. August 12 – 19: 2018 Junior League World Series in Taylor at Heritage Park The Shing-Ming Junior LL (Asia-Pacific) defeated the Lufkin LL (Southwest), 2–0, in the final. August 16 – 26: 2018 Little League World Series in South Williamsport at both the Little League Volunteer Stadium and the Howard J. Lamade Stadium The Honolulu LL (West) defeated the South Seoul LL (Asia-Pacific and Middle East), 3–0, in the final.
The first step in the NADP-ME type C4 pathway is the conversion of pyruvate (Pyr) to phosphoenolpyruvate (PEP), by the enzyme Pyruvate phosphate dikinase (PPDK). This reaction requires inorganic phosphate and ATP plus pyruvate, producing PEP, AMP, and inorganic pyrophosphate (PPi). The next step is the carboxylation of PEP by the PEP carboxylase enzyme (PEPC) producing oxaloacetate. Both of these steps occur in the mesophyll cells: pyruvate + Pi + ATP → PEP + AMP + PPi PEP + CO2 → oxaloacetate PEPC has a low KM for HCO−3 — and, hence, high affinity, and is not confounded by O2 thus it will work even at low concentrations of CO2. The product is usually converted to malate (M), which diffuses to the bundle-sheath cells surrounding a nearby vein. Here, it is decarboxylated by the NADP-malic enzyme (NADP-ME) to produce CO2 and pyruvate. The CO2 is fixed by RuBisCo to produce phosphoglycerate (PGA) while the pyruvate is transported back to the mesophyll cell, together with about half of the phosphoglycerate (PGA). This PGA is chemically reduced in the mesophyll and diffuses back to the bundle sheath where it enters the conversion phase of the Calvin cycle. For each CO2 molecule exported to the bundle sheath the malate shuttle transfers two electrons, and therefore reduces the demand of reducing power in the bundle sheath.
Sources: en.wikipedia.org
July 28 – August 4: 2018 Senior League Baseball World Series in Easley at Easley Recreation Complex The Pariba Little League (Caribbean) defeated the Naamans Little League (East), 7–2, in the final. July 29 – August 5: 2018 Little League Intermediate (50/70) Baseball World Series in Livermore at Max Baer Park The West Seoul LL (Asia-Pacific) defeated the Livermore/Granada LL (Host), 10–0, in the final. August 12 – 19: 2018 Junior League World Series in Taylor at Heritage Park The Shing-Ming Junior LL (Asia-Pacific) defeated the Lufkin LL (Southwest), 2–0, in the final. August 16 – 26: 2018 Little League World Series in South Williamsport at both the Little League Volunteer Stadium and the Howard J. Lamade Stadium The Honolulu LL (West) defeated the South Seoul LL (Asia-Pacific and Middle East), 3–0, in the final.
January 19 – March 25: 2018 FIBA Americas League San Lorenzo defeated Mogi das Cruzes, 79–71, to win their first FIBA Americas League title. Regatas Corrientes took third place. June 11 – 16: 2018 FIBA Under-18 Americas Championship in St. Catharines The United States defeated Canada, 113–74, to win their fifth consecutive and ninth overall FIBA Under-18 Americas Championship title. Argentina took third place. August 1 – 7: 2018 FIBA Under-18 Women's Americas Championship in Mexico City The United States defeated Canada, 84–60, to win their ninth consecutive and tenth overall FIBA Under-18 Women's Americas Championship title. Argentina took third place.
The strong tornado widened again and curved northward as it exited Hodonín and moved into a rural area, completely mowing down a large swath of trees as it impacted a patch of forest. Metal truss transmission towers were blown over in this area, crops were damaged in farm fields, and damage along this segment of the path was rated F2. The tornado briefly strengthened again one final time as it struck the village of Pánov at high-end F3 strength. Almost every structure in the small village was damaged in some way, and multiple homes were significantly damaged or destroyed, a few of which were leveled. Outbuildings were destroyed, cars were damaged by flying debris, and large trees were snapped and denuded as well. The tornado continued past Pánov and moved through another densely forested area, weakening back to F2 strength as it flattened another large swath of trees. The tornado continued to weaken, and trees beyond this point were downed at F1 intensity as the tornado continued to the northeast before it abruptly dissipated near Ratíškovice. In all, at least 1,200 buildings were damaged or destroyed by the tornado along its 27.1 kilometer (17 mi)-long path. 6 people were killed by the tornado, and at least 200 more were injured, some critically.
5-HEDH is an NADPH dehydrogenase oxidoreductase enzyme. It transfers a hydrogen cation (or hydron) H+ from 5(S)-hydroxy (i.e. 5(S)-OH) residues of its fatty acid targets to nicotinamide adenine dinucleotide phosphate+ (NADP+) to form 5-oxo (i.e. 5-O=) counterparts of its targets plus reduced NADP+, i.e. NADPH. The reaction (where R indicates a long chain [14 or more carbons] fatty acid) is: NADP+ + 5(S)-hydroxy fatty acid (i.e. 5(S)-OH-R) ⇌ {\displaystyle \rightleftharpoons } NADPH + H+ + oxo fatty acid (i.e. 5-O=R) The reaction appears to follow a ping-pong mechanism. It is fully reversible, readily converting 5-oxo targets to their corresponding 5(S)-hydroxy counterparts. The direction of this reaction is dependent on the level of NADP+ relative to that of NADPH: The immediate metabolic precursor to 5(S)-HETE, 5(S)-hydroperoxy-6S,8Z,11Z,14Z-eicosatetraenoic acid 5(S)-HpETE, can be converted to 5-oxo-ETE in a non-enzymatic dehydration reaction or chemical lipid peroxidation reactions. The physiological occurrence and relevancy of these reaction pathways has not been ascertained.
January 19 – March 25: 2018 FIBA Americas League San Lorenzo defeated Mogi das Cruzes, 79–71, to win their first FIBA Americas League title. Regatas Corrientes took third place. June 11 – 16: 2018 FIBA Under-18 Americas Championship in St. Catharines The United States defeated Canada, 113–74, to win their fifth consecutive and ninth overall FIBA Under-18 Americas Championship title. Argentina took third place. August 1 – 7: 2018 FIBA Under-18 Women's Americas Championship in Mexico City The United States defeated Canada, 84–60, to win their ninth consecutive and tenth overall FIBA Under-18 Women's Americas Championship title. Argentina took third place.
Sources: en.wikipedia.org
The plus sign indicates the oxidized form of nicotinamide adenine dinucleotide, which can accept electrons. When it accepts electrons, it becomes NADH. The two forms together support redox reactions in cells.
No. NAD+ is the oxidized form and NADH is the reduced form. They differ by two electrons and a proton equivalent, and cells interconvert them during metabolism.
Yes. NAD+ is present in all living cells and is required for fundamental metabolic reactions. Its concentration varies by tissue, compartment, and time.
NAD+ is a coenzyme found in living cells and is the oxidized form of nicotinamide adenine dinucleotide. It accepts electrons in redox reactions and also serves as a substrate for certain signaling and repair enzymes.