NAD metabolic process

Definition

Target type: biologicalprocess

The chemical reactions and pathways involving nicotinamide adenine dinucleotide (NAD), a coenzyme present in most living cells and derived from the B vitamin nicotinic acid. [GOC:jl, ISBN:0618254153]

NAD metabolic process encompasses a series of biochemical reactions that involve the synthesis, degradation, and utilization of nicotinamide adenine dinucleotide (NAD). NAD is a crucial coenzyme involved in numerous metabolic pathways, playing a vital role in energy production, redox reactions, and signaling cascades. The NAD metabolic process can be broadly categorized into two main stages: NAD biosynthesis and NAD degradation.

**NAD biosynthesis:**

* **De novo synthesis:** This pathway involves the conversion of tryptophan or nicotinic acid (niacin) into nicotinamide mononucleotide (NMN). NMN is then phosphorylated to NAD by the enzyme NMN adenylyltransferase.
* **Precursor salvage pathway:** This pathway utilizes pre-existing nicotinamide, nicotinic acid, or nicotinamide riboside to produce NAD. These precursors are salvaged and converted to NAD through specific enzymatic reactions.

**NAD degradation:**

* NAD is degraded into nicotinamide, which can be recycled back into the biosynthesis pathway.
* NAD can also be hydrolyzed to nicotinamide riboside and adenosine diphosphate ribose (ADPR). ADPR can be further metabolized into ADP-ribose, a signaling molecule involved in various cellular processes.

**Functions of NAD:**

* **Redox reactions:** NAD acts as an electron carrier in numerous redox reactions, including glycolysis, the citric acid cycle, and oxidative phosphorylation. It shuttles electrons between different metabolic pathways, facilitating energy production.
* **DNA repair:** NAD is a substrate for poly(ADP-ribose) polymerase (PARP), an enzyme involved in DNA damage repair. PARP utilizes NAD to generate poly(ADP-ribose) chains, which contribute to the repair process.
* **Signaling pathways:** NAD is involved in various signaling pathways, including the regulation of calcium homeostasis, apoptosis, and cell proliferation.

**Regulation of NAD metabolism:**

* NAD levels are tightly regulated by various factors, including nutritional intake, metabolic stress, and hormonal signals.
* Enzymes involved in NAD biosynthesis and degradation are subject to regulation by various mechanisms, ensuring optimal NAD levels for cellular function.

**Clinical implications:**

* NAD metabolism is linked to various diseases, including cancer, neurodegenerative disorders, and metabolic diseases.
* Therapeutic strategies targeting NAD metabolism are being investigated for the treatment of these diseases.

Overall, NAD metabolic process plays a critical role in maintaining cellular function and homeostasis. Its intricate regulation ensures the optimal availability of NAD for various metabolic pathways and signaling cascades, highlighting its importance in human health.'
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Proteins (5)

Compounds (36)