Visfatin (NAMPT) Human Active Protein

This gene encodes a protein that catalyzes the condensation of nicotinamide with 5-phosphoribosyl-1-pyrophosphate to yield nicotinamide mononucleotide, one step in the biosynthesis of nicotinamide adenine dinucleotide. The protein belongs to the nicotinic acid phosphoribosyltransferase (NAPRTase) family and is thought to be involved in many important biological processes, including metabolism, stress response and aging. This gene has a pseudogene on chromosome 10. [provided by RefSeq, Feb 2011]

Function: Catalyzes the condensation of nicotinamide with 5-phosphoribosyl-1-pyrophosphate to yield nicotinamide mononucleotide, an intermediate in the biosynthesis of NAD. It is the rate limiting component in the mammalian NAD biosynthesis pathway. The secreted form behaves both as a cytokine with immunomodulating properties and an adipokine with anti-diabetic properties, it has no enzymatic activity, partly because of lack of activation by ATP, which has a low level in extracellular space and plasma. Ref.10

Catalytic activity: Nicotinamide D-ribonucleotide + diphosphate = nicotinamide + 5-phospho-alpha-D-ribose 1-diphosphate.

Enzyme regulation: Inhibited by FK866. FK866 competes for the same binding site as nicotinamide, but due to its very low dissociation rate, it is essentially an irreversible inhibitor. Ref.11

Pathway: Cofactor biosynthesis; NAD(+) biosynthesis; nicotinamide D-ribonucleotide from 5-phospho-alpha-D-ribose 1-diphosphate and nicotinamide: step 1/1.

Subunit structure: Homodimer. Ref.11

Subcellular location: Nucleus. Cytoplasm

By similarity. Secreted. Note: Under non-inflammatory conditions, visfatin predominantly exhibits a granular pattern within the nucleus. Secreted by endothelial cells upon IL-1beta stimulation. Abundantly secreted in milk, reaching 100-fold higher concentrations compared to maternal serum. Ref.9 Ref.10

Tissue specificity: Expressed in large amounts in bone marrow, liver tissue, and muscle. Also present in heart, placenta, lung, and kidney tissues.

Sequence similarities: Belongs to the NAPRTase family.

Sequence caution: The sequence AAQ96862.1 differs from that shown. Reason: Erroneous gene model prediction. The sequence EAL24400.1 differs from that shown. Reason: Erroneous gene model prediction.