Poster: Enzymology
Abs #
255: D-pantoate supply is rate-limiting in pantothenate synthesis in leaves.
Pantothenate, vitamin B5, is the metabolic precursor of coenzyme A. The synthetic pathway to pantothenate has been well characterized in microbes but the enzymes in the plant pathway have not been studied in detail, except the last step of ATP-dependent ligation of pantoate and b-alanine to synthesize pantothenate. We investigated the effect of an exogenous supply of 1 mM b-alanine or 1 mM pantoyllactone (a precursor of d-pantoate) for 12h, on the pantothenate pools in excised leaves of Limonium latifolium, tomato, bean and grapefruit. In all of these species, significantly higher levels of extractable pantothenic acid were found when pantoyllactone was supplied, but not when b-alanine was supplied. Radiolabeled b-alanine was employed to verify that its uptake was not affected. Our results suggested that pantoate supply is rate-limiting for pantothenate synthesis in leaves. Using bacterial gene sequences, we have identified Arabidopsis thaliana genes coding for enzymes potentially involved in pantoate synthesis. Sequence tagged T-DNA insertion mutants for select Arabidopsis genes were characterized to establish the role of these enzymes in the production of pantoate and pantothenate.
