Nicotinamide Phosphoribosyltransferase/Visfatin Does Not Catalyze Nicotinamide Mononucleotide Formation in Blood Plasma

Nicotinamide (Nam) phosphoribosyltransferase (NAMPT) is the rate-limiting enzyme in mammalian NAD synthesis, catalyzing nicotinamide mononucleotide (NMN) formation from Nam and 5-phosphoribosyl 1-pyrophosphate (PRPP). NAMPT has also been described as an adipocytokine visfatin with a variety of actio...

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Main Authors:	Hara, Nobumasa, Yamada, Kazuo, Shibata, Tomoko, Osago, Harumi, Tsuchiya, Mikako
Format:	Online
Language:	English
Published:	Public Library of Science 2011
Online Access:	https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3149623/

id	pubmed-3149623
recordtype	oai_dc
spelling	pubmed-31496232011-08-08 Nicotinamide Phosphoribosyltransferase/Visfatin Does Not Catalyze Nicotinamide Mononucleotide Formation in Blood Plasma Hara, Nobumasa Yamada, Kazuo Shibata, Tomoko Osago, Harumi Tsuchiya, Mikako Research Article Nicotinamide (Nam) phosphoribosyltransferase (NAMPT) is the rate-limiting enzyme in mammalian NAD synthesis, catalyzing nicotinamide mononucleotide (NMN) formation from Nam and 5-phosphoribosyl 1-pyrophosphate (PRPP). NAMPT has also been described as an adipocytokine visfatin with a variety of actions, although physiological significance of this protein remains unclear. It has been proposed that possible actions of visfatin are mediated through the extracellular formation of NMN. However, we did not detect NMN in mouse blood plasma, even with a highly specific and sensitive liquid chromatography/tandem mass spectrometry. Furthermore, there is no or little ATP, the activator of NAMPT, in extracellular spaces. We thus questioned whether visfatin catalyzes the in situ formation of NMN under such extracellular milieus. To address this question, we here determined Km values for the substrates Nam and PRPP in the NAMPT reaction without or with ATP using a recombinant human enzyme and found that 1 mM ATP dramatically decreases Km values for the substrates, in particular PRPP to its intracellular concentration. Consistent with the kinetic data, only when ATP is present at millimolar levels, NAMPT efficiently catalyzed the NMN formation at the intracellular concentrations of the substrates. Much lower concentrations of Nam and almost the absence of PRPP and ATP in the blood plasma suggest that NAMPT should not efficiently catalyze its reaction under the extracellular milieu. Indeed, NAMPT did not form NMN in the blood plasma. From these kinetic analyses of the enzyme and quantitative determination of its substrates, activator, and product, we conclude that visfatin does not participate in NMN formation under the extracellular milieus. Together with the absence of NMN in the blood plasma, our conclusion does not support the concept of “NAMPT-mediated systemic NAD biosynthesis.” Our study would advance current understanding of visfatin physiology. Public Library of Science 2011-08-03 /pmc/articles/PMC3149623/ /pubmed/21826208 http://dx.doi.org/10.1371/journal.pone.0022781 Text en Hara et al. http://creativecommons.org/licenses/by/4.0/ This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are properly credited.
repository_type	Open Access Journal
institution_category	Foreign Institution
institution	US National Center for Biotechnology Information
building	NCBI PubMed
collection	Online Access
language	English
format	Online
author	Hara, Nobumasa Yamada, Kazuo Shibata, Tomoko Osago, Harumi Tsuchiya, Mikako
spellingShingle	Hara, Nobumasa Yamada, Kazuo Shibata, Tomoko Osago, Harumi Tsuchiya, Mikako Nicotinamide Phosphoribosyltransferase/Visfatin Does Not Catalyze Nicotinamide Mononucleotide Formation in Blood Plasma
author_facet	Hara, Nobumasa Yamada, Kazuo Shibata, Tomoko Osago, Harumi Tsuchiya, Mikako
author_sort	Hara, Nobumasa
title	Nicotinamide Phosphoribosyltransferase/Visfatin Does Not Catalyze Nicotinamide Mononucleotide Formation in Blood Plasma
title_short	Nicotinamide Phosphoribosyltransferase/Visfatin Does Not Catalyze Nicotinamide Mononucleotide Formation in Blood Plasma
title_full	Nicotinamide Phosphoribosyltransferase/Visfatin Does Not Catalyze Nicotinamide Mononucleotide Formation in Blood Plasma
title_fullStr	Nicotinamide Phosphoribosyltransferase/Visfatin Does Not Catalyze Nicotinamide Mononucleotide Formation in Blood Plasma
title_full_unstemmed	Nicotinamide Phosphoribosyltransferase/Visfatin Does Not Catalyze Nicotinamide Mononucleotide Formation in Blood Plasma
title_sort	nicotinamide phosphoribosyltransferase/visfatin does not catalyze nicotinamide mononucleotide formation in blood plasma
description	Nicotinamide (Nam) phosphoribosyltransferase (NAMPT) is the rate-limiting enzyme in mammalian NAD synthesis, catalyzing nicotinamide mononucleotide (NMN) formation from Nam and 5-phosphoribosyl 1-pyrophosphate (PRPP). NAMPT has also been described as an adipocytokine visfatin with a variety of actions, although physiological significance of this protein remains unclear. It has been proposed that possible actions of visfatin are mediated through the extracellular formation of NMN. However, we did not detect NMN in mouse blood plasma, even with a highly specific and sensitive liquid chromatography/tandem mass spectrometry. Furthermore, there is no or little ATP, the activator of NAMPT, in extracellular spaces. We thus questioned whether visfatin catalyzes the in situ formation of NMN under such extracellular milieus. To address this question, we here determined Km values for the substrates Nam and PRPP in the NAMPT reaction without or with ATP using a recombinant human enzyme and found that 1 mM ATP dramatically decreases Km values for the substrates, in particular PRPP to its intracellular concentration. Consistent with the kinetic data, only when ATP is present at millimolar levels, NAMPT efficiently catalyzed the NMN formation at the intracellular concentrations of the substrates. Much lower concentrations of Nam and almost the absence of PRPP and ATP in the blood plasma suggest that NAMPT should not efficiently catalyze its reaction under the extracellular milieu. Indeed, NAMPT did not form NMN in the blood plasma. From these kinetic analyses of the enzyme and quantitative determination of its substrates, activator, and product, we conclude that visfatin does not participate in NMN formation under the extracellular milieus. Together with the absence of NMN in the blood plasma, our conclusion does not support the concept of “NAMPT-mediated systemic NAD biosynthesis.” Our study would advance current understanding of visfatin physiology.
publisher	Public Library of Science
publishDate	2011
url	https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3149623/
_version_	1611469032594079744

Nicotinamide Phosphoribosyltransferase/Visfatin Does Not Catalyze Nicotinamide Mononucleotide Formation in Blood Plasma

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