title: Metabolic profiling of alternative NAD biosynthetic routes in mouse tissues.
abstract: NAD plays essential redox and non-redox roles in cell biology. In mammals, its de novo and recycling biosynthetic pathways encompass two independent branches, the "amidated" and "deamidated" routes. Here we focused on the indispensable enzymes gating these two routes, i.e. nicotinamide mononucleotide adenylyltransferase (NMNAT), which in mammals comprises three distinct isozymes, and NAD synthetase (NADS). First, we measured the in vitro activity of the enzymes, and the levels of all their substrates and products in a number of tissues from the C57BL/6 mouse. Second, from these data, we derived in vivo estimates of enzymes'rates and quantitative contributions to NAD homeostasis. The NMNAT activity, mainly represented by nuclear NMNAT1, appears to be high and nonrate-limiting in all examined tissues, except in blood. The NADS activity, however, appears rate-limiting in lung and skeletal muscle, where its undetectable levels parallel a relative accumulation of the enzyme's substrate NaAD (nicotinic acid adenine dinucleotide). In all tissues, the amidated NAD route was predominant, displaying highest rates in liver and kidney, and lowest in blood. In contrast, the minor deamidated route showed higher relative proportions in blood and small intestine, and higher absolute values in liver and small intestine. Such results provide the first comprehensive picture of the balance of the two alternative NAD biosynthetic routes in different mammalian tissues under physiological conditions. This fills a gap in the current knowledge of NAD biosynthesis, and provides a crucial information for the study of NAD metabolism and its role in disease.
authors.affiliation: Department of Clinical Sciences, Section of Biochemistry, Polytechnic University of Marche, Ancona, Italy.
authors.forename: Valerio
authors.initials: V
authors.lastname: Mori
authors.affiliation: Department of Clinical Sciences, Section of Biochemistry, Polytechnic University of Marche, Ancona, Italy.
authors.forename: Adolfo
authors.initials: A
authors.lastname: Amici
authors.affiliation: Department of Clinical Sciences, Section of Biochemistry, Polytechnic University of Marche, Ancona, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Mazzola
authors.affiliation: School of Life Sciences, University of Nottingham, Medical School, Queen's Medical Centre, Nottingham, United Kingdom.
authors.forename: Michele
authors.initials: M
authors.lastname: Di Stefano
authors.affiliation: School of Life Sciences, University of Nottingham, Medical School, Queen's Medical Centre, Nottingham, United Kingdom.
authors.forename: Laura
authors.initials: L
authors.lastname: Conforti
authors.affiliation: School of Biosciences and Biotechnology, University of Camerino, Camerino, Italy.
authors.forename: Giulio
authors.initials: G
authors.lastname: Magni
authors.affiliation: Department of Agricultural, Food and Environmental Sciences, Polytechnic University of Marche, Ancona, Italy.
authors.forename: Silverio
authors.initials: S
authors.lastname: Ruggieri
authors.affiliation: Department of Agricultural, Food and Environmental Sciences, Polytechnic University of Marche, Ancona, Italy.
authors.forename: Nadia
authors.initials: N
authors.lastname: Raffaelli
authors.affiliation: Department of Clinical Sciences, Section of Biochemistry, Polytechnic University of Marche, Ancona, Italy.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Orsomando
mesh_terms: D000818:Animals; D051379:Mice; D008810:Mice, Inbred C57BL; D009243:NAD / Q000031:analogs & derivatives / Q000096:biosynthesis* / Q000378:metabolism; D009612:Nicotinamide-Nucleotide Adenylyltransferase / Q000378:metabolism
chemical_list: D009243:NAD; C018348:nicotinic acid adenine dinucleotide; D009612:Nicotinamide-Nucleotide Adenylyltransferase