Early steps in the biosynthesis of NAD in Arabidopsis start with aspartate and occur in the plastid.
NAD is a ubiquitous coenzyme involved in oxidation-reduction reactions and is synthesized by way of quinolinate. Animals and some bacteria synthesize quinolinate from tryptophan, whereas other bacteria synthesize quinolinate from aspartate (Asp) using L-Asp oxidase and quinolinate synthase. We show here that Arabidopsis (Arabidopsis thaliana) uses the Asp-to-quinolinate pathway. The Arabidopsis L-Asp oxidase or quinolinate synthase gene complemented the Escherichia coli mutant defective in the corresponding gene, and T-DNA-based disruption of either of these genes, as well as of the gene coding for the enzyme quinolinate phosphoribosyltransferase, was embryo lethal. An analysis of functional green fluorescent protein-fused constructs and in vitro assays of uptake into isolated chloroplasts demonstrated that these three enzymes are located in the plastid.
Katoh
Akira
A
Graduate School of Biological Sciences, Nara Institute of Science and Technology, Ikoma, Nara 630-0192, Japan.
Uenohara
Kazuya
K
Akita
Mitsuru
M
Hashimoto
Takashi
T
D000594:Amino Acid Oxidoreductases / Q000378:metabolism / Q000502:physiology; D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D001224:Aspartic Acid / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics; D029968:Escherichia coli Proteins; D009097:Multienzyme Complexes / Q000378:metabolism / Q000502:physiology; D009243:NAD / Q000096:biosynthesis*; D010430:Pentosyltransferases / Q000378:metabolism / Q000502:physiology; D018087:Plastids / Q000378:metabolism*; D017378:Quinolinic Acid / Q000378:metabolism; D000098553:Nicotinate-Nucleotide Diphosphorylase (Carboxylating)
D029968:Escherichia coli Proteins; D009097:Multienzyme Complexes; D009243:NAD; D001224:Aspartic Acid; C022512:quinolinic acid synthetase; D000594:Amino Acid Oxidoreductases; C031955:L-aspartate oxidase, E coli; D010430:Pentosyltransferases; D000098553:Nicotinate-Nucleotide Diphosphorylase (Carboxylating); D017378:Quinolinic Acid