Target type: biologicalprocess
The chemical reactions and pathways resulting in the breakdown of nicotinamide adenine dinucleotide, a coenzyme present in most living cells and derived from the B vitamin nicotinic acid; catabolism may be of either the oxidized form, NAD, or the reduced form, NADH. [GOC:jl, ISBN:0618254153]
NAD catabolic process is a fundamental biochemical pathway that involves the breakdown of nicotinamide adenine dinucleotide (NAD), a key coenzyme involved in various metabolic reactions. NAD exists in two forms: oxidized (NAD+) and reduced (NADH). The catabolism of NAD primarily occurs in the following steps:
1. **Hydrolysis:** NAD is initially hydrolyzed by NAD glycohydrolase, cleaving the molecule into nicotinamide and ADP-ribose.
2. **Nicotinamide Degradation:** Nicotinamide is further degraded through several enzymatic steps, including:
- **Nicotinamidase:** This enzyme removes the carboxamide group from nicotinamide, yielding nicotinic acid (niacin).
- **Nicotinic acid mononucleotide (NAMN) synthetase:** This enzyme converts nicotinic acid to NAMN.
- **Quinolinate phosphoribosyltransferase:** This enzyme catalyzes the conversion of NAMN to quinolinate.
3. **ADP-ribose Degradation:** ADP-ribose can undergo various metabolic pathways, including:
- **ADP-ribose pyrophosphatase:** This enzyme hydrolyzes ADP-ribose to AMP and ribose-5-phosphate.
- **ADP-ribose reductase:** This enzyme reduces ADP-ribose to deoxy-ADP-ribose.
4. **Quinolinate Metabolism:** Quinolinate is further metabolized via the kynurenine pathway, leading to the production of NAD precursors, such as nicotinamide.
The NAD catabolic process plays a crucial role in regulating NAD levels within the cell. It is tightly controlled by various feedback mechanisms and is essential for maintaining redox balance, energy production, and other cellular functions. Furthermore, disruptions in NAD catabolism have been implicated in several disease states, including cancer, neurodegenerative disorders, and metabolic disorders.
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| Protein | Definition | Taxonomy |
|---|---|---|
| NAD(+) hydrolase SARM1 | An NAD(+) hydrolase SARM1 that is encoded in the genome of human. [PRO:CNA] | Homo sapiens (human) |
| Compound | Definition | Classes | Roles |
|---|---|---|---|
| niacinamide | nicotinamide : A pyridinecarboxamide that is pyridine in which the hydrogen at position 3 is replaced by a carboxamide group. | pyridine alkaloid; pyridinecarboxamide; vitamin B3 | anti-inflammatory agent; antioxidant; cofactor; EC 2.4.2.30 (NAD(+) ADP-ribosyltransferase) inhibitor; EC 3.5.1.98 (histone deacetylase) inhibitor; Escherichia coli metabolite; geroprotector; human urinary metabolite; metabolite; mouse metabolite; neuroprotective agent; Saccharomyces cerevisiae metabolite; Sir2 inhibitor |
| rabeprazole | Rabeprazole: A 4-(3-methoxypropoxy)-3-methylpyridinyl derivative of timoprazole that is used in the therapy of STOMACH ULCERS and ZOLLINGER-ELLISON SYNDROME. The drug inhibits H(+)-K(+)-EXCHANGING ATPASE which is found in GASTRIC PARIETAL CELLS. | benzimidazoles; pyridines; sulfoxide | anti-ulcer drug; EC 3.6.3.10 (H(+)/K(+)-exchanging ATPase) inhibitor |
| phenazopyridine hydrochloride | phenazopyridine hydrochloride : A hydrochloride obtained by combining phenazopyridine with one equivalent of hydrochloric acid. A local anesthetic that has topical analgesic effect on mucosa lining of the urinary tract. Its use is limited by problems with toxicity (primarily blood disorders) and potential carcinogenicity. | hydrochloride | carcinogenic agent; local anaesthetic; non-narcotic analgesic |
| Berberine chloride (TN) | organic molecular entity | ||
| tenatoprazole | Tenatoprazole: structure in first source | imidazopyridine | |
| nitrofurazone | nitrofurazone : A semicarbazone resulting from the formal condensation of semicarbazide with 5-nitrofuraldehyde. A broad spectrum antibacterial drug, although with little activity against Pseudomonas species, it is used as a local application for burns, ulcers, wounds and skin infections. Nitrofurazone: A topical anti-infective agent effective against gram-negative and gram-positive bacteria. It is used for superficial WOUNDS AND INJURIES and skin infections. Nitrofurazone has also been administered orally in the treatment of TRYPANOSOMIASIS. | ||
| dexlansoprazole | Dexlansoprazole: The R-isomer of lansoprazole that is used to treat severe GASTROESOPHAGEAL REFLUX DISEASE. | benzimidazoles; sulfoxide |