Formate dehydrogenase in Arabidopsis thaliana: characterization and possible targeting to the chloroplast

Formate dehydrogenase (E.C. 1.2.1.2) is a mitochondrial-localized NAD-requi ring enzyme in green plants. The enzyme activity and corresponding mRNA in leaves of Arabinopsis thaliana are induced by treatment with one-carbon met abolites. The cDNA for the Arabidopsis formate dehydrogenase is similar to that of other plants except for the N-terminal region, which is predicted t o target chloroplasts as well as mitochondria. The specific of activity of the enzyme in isolated chloroplasts suggests it is targeted to both mitocho ndria and chloroplasts in Arabidopsis. Formate dehydrogenase from Arabidops is was partially purified and K-m values for formate and NAD(+) were determ ined to be 10 mM and 65 muM, respectively; the K-i for NADH was 17 muM. We conclude that formate dehydrogenase is normally present in Arabidopsis chlo roplasts and that sensitivity to inhibition by NADH may play a role in whet her cellular formate is assimilated or dissimilated. (C) 2000 Elsevier Scie nce Ireland Ltd. All rights reserved.