nicotinamide phosphoribosyltransferase activity

Definition

Target type: molecularfunction

Catalysis of the reaction: diphosphate + nicotinamide mononucleotide = 5-phospho-alpha-D-ribose 1-diphosphate + H+ + nicotinamide. [RHEA:16149]

Nicotinamide phosphoribosyltransferase (NAMPT) is an enzyme that catalyzes the synthesis of nicotinamide adenine dinucleotide (NAD+) from nicotinamide and 5-phosphoribosyl 1-pyrophosphate (PRPP). NAD+ is a critical coenzyme involved in various metabolic reactions, including redox reactions, DNA repair, and signal transduction.

NAMPT plays a crucial role in the salvage pathway of NAD+ biosynthesis, which recovers nicotinamide, a breakdown product of NAD+, for NAD+ regeneration. This pathway is particularly important in tissues with high NAD+ demand, such as the brain, liver, and adipose tissue.

The molecular function of NAMPT involves several key steps:

1. **Binding of substrates:** NAMPT binds to both nicotinamide and PRPP, bringing them together in the active site.

2. **Phosphoribosylation:** NAMPT catalyzes the transfer of the phosphoribosyl group from PRPP to nicotinamide, forming nicotinamide mononucleotide (NMN). This reaction is highly specific and requires Mg2+ as a cofactor.

3. **Product release:** NMN is released from the active site of NAMPT, leaving the enzyme ready for another cycle.

4. **Regulation:** NAMPT activity is regulated by various factors, including NAD+ levels, intracellular calcium concentrations, and post-translational modifications.

5. **Cellular localization:** NAMPT can be found in both the cytoplasm and the nucleus, suggesting that it may have different functions in different cellular compartments.

In summary, NAMPT's molecular function is essential for maintaining NAD+ levels, which are crucial for numerous cellular processes. Its activity is tightly regulated and plays a significant role in various physiological and pathological conditions.'
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Proteins (2)

Compounds (8)