Pyridine dinucleotides are key redox carriers in the soluble phase of all living cells, and both NAD+ and NADP+ play crucial roles in pro-oxidant and antioxidant metabolism. The capacity of cells to modulate the NAD(P)H/NAD(P)+ ratio is thus critical not only for central redox control of metabolism but also for preemptive management of oxidative stress. Recent studies show that NAD+ and NADP+ can be utilized to produce a number of metabolites important in cell signalling. Other reactions that consume NAD+ include protein de-acetylation and poly ADP-ribosylation. These developments bring a significant amount of additional interest to the investigation of cellular NAD+ biosynthesis and regulation. Relatively little is known about NAD+ synthesis in plants. Comparative genomics suggests that plants form NAD+ through de novo synthesis from quinolinate, as well as by a salvage pathway that reuses nicotinamide released from NAD+. NADP+ is produced by phosphorylation of NAD+ The purpose of our work was to verify the presence of mitochondrial Nicotinamide mononucleotide adenylyl-transferase (NMN-AT), that catalyzes the reversible reaction NMN+ ATP NAD+ + PPi NMN was added to mitochondria isolated from aged-dehydrated slices tubers of Helianthus tuberosus and NAD(P)+ synthesis was tested by means of HPLC experiments. The dependence of NAD(P)+ synthesis rate on NMN concentration was studied. Hyperbolic dependence of the reaction rate on NMN concentration was found and was inhibited by PPi and AMP. The characterization of NMN-AT provided compelling evidence that NAD+ biosynthesis pathways may exist in plant mitochondria.

Existence of intramitochondrial nicotinamide mononucleotide adenylyl-transferase activity, which allows for NAD+ synthesis from NMN and endogenous ATP in aged-dehydrated slices tubers of Helianthus tuberosus

PALLOTTA, Maria Luigia;
2007

Abstract

Pyridine dinucleotides are key redox carriers in the soluble phase of all living cells, and both NAD+ and NADP+ play crucial roles in pro-oxidant and antioxidant metabolism. The capacity of cells to modulate the NAD(P)H/NAD(P)+ ratio is thus critical not only for central redox control of metabolism but also for preemptive management of oxidative stress. Recent studies show that NAD+ and NADP+ can be utilized to produce a number of metabolites important in cell signalling. Other reactions that consume NAD+ include protein de-acetylation and poly ADP-ribosylation. These developments bring a significant amount of additional interest to the investigation of cellular NAD+ biosynthesis and regulation. Relatively little is known about NAD+ synthesis in plants. Comparative genomics suggests that plants form NAD+ through de novo synthesis from quinolinate, as well as by a salvage pathway that reuses nicotinamide released from NAD+. NADP+ is produced by phosphorylation of NAD+ The purpose of our work was to verify the presence of mitochondrial Nicotinamide mononucleotide adenylyl-transferase (NMN-AT), that catalyzes the reversible reaction NMN+ ATP NAD+ + PPi NMN was added to mitochondria isolated from aged-dehydrated slices tubers of Helianthus tuberosus and NAD(P)+ synthesis was tested by means of HPLC experiments. The dependence of NAD(P)+ synthesis rate on NMN concentration was studied. Hyperbolic dependence of the reaction rate on NMN concentration was found and was inhibited by PPi and AMP. The characterization of NMN-AT provided compelling evidence that NAD+ biosynthesis pathways may exist in plant mitochondria.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11695/13913
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