High impact information on NPT1

• This extension was not observed in strains mutant for SIR2 (which encodes the silencing protein Sir2p) or NPT1 (a gene in a pathway in the synthesis of NAD, the oxidized form of nicotinamide adenine dinucleotide) [1].
• We show that Npt1 and a previously uncharacterized salvage pathway enzyme, Nma2, are both concentrated in the nucleus, indicating that a significant amount of NAD(+) is regenerated in this organelle [2].
• Using purified nicotinate phosphoribosyltransferase, the enzyme-catalyzed formation of nicotinate mononucleotide was analyzed using a new high pressure liquid chromatographic assay (Hanna, L., and Sloan, D [3].
• In addition, this assay procedure was used to demonstrate that purified nicotinate phosphoribosyltransferase possesses an ATPase activity in the presence of either product (pyrophosphate or nicotinate mononucleotide (NaMN] but in the absence of 5-phosphoribosyl alpha-1-pyrophosphate (P-Rib-PP) [3].
• A new procedure has been designed for the purification of nicotinate phosphoribosyltransferase and orotate phosphoribosyltransferase from the same baker's yeast extract [3].

Biological context of NPT1

• Both NPT1 and SIR2 provide resistance against heat shock, demonstrating that these genes act in a more general manner to promote cell survival [2].
• The overall NAPRTase reaction involves phosphorylation of a low-affinity form of the enzyme by ATP, followed by generation of a high-affinity form of the enzyme, which then binds substrates and produces NAMN [4].

Associations of NPT1 with chemical compounds

• We now show that mutation of a highly conserved histidine residue in Npt1p results in a silencing defect, indicating that Npt1p enzymatic activity is required for silencing [5].
• In Saccharomyces cerevisiae the nicotinic acid moiety of NAD+ can be synthesized from tryptophan using the kynurenine pathway or incorporated directly using nicotinate phosphoribosyl transferase (NPT1) [6].

Regulatory relationships of NPT1

• Although SIR2-dependent processes are enhanced by additional NPT1, steady-state NAD(+) levels and NAD(+)/NADH ratios remain unaltered [2].

Analytical, diagnostic and therapeutic context of NPT1

• Kinetic analysis of nicotinate phosphoribosyltransferase from yeast using high pressure liquid chromatography [3].

References