Early Steps in the Biosynthesis of NAD in Arabidopsis Start with Aspartate and Occur in the Plastid

摘要: NAD is a ubiquitous coenzyme involved in oxidation-reduction reactions and synthesized by way of quinolinate. Animals some bacteria synthesize quinolinate from tryptophan, whereas other aspartate (Asp) using L-Asp oxidase synthase. We show here that Arabidopsis (Arabidopsis thaliana) uses the Asp-to-quinolinate pathway. The or synthase gene complemented Escherichia coli mutant defective corresponding gene, T-DNA-based disruption either these genes, as well coding for enzyme phosphoribosyltransferase, was embryo lethal. An analysis functional green fluorescent protein-fused constructs vitro assays uptake into isolated chloroplasts demonstrated three enzymes are located plastid.