Biochemical and physiological characterization of Arabidopsis thaliana AtCoAse: a Nudix CoA hydrolyzing protein...

CoA is required for many synthetic and degradative reactions in intermediary metabolism and is the principal acyl carrier in prokaryotic and eukaryotic cells. CoA is synthesized in five steps from pantothenate, and recently, the CoA biosynthetic genes of Arabidopsis have all been identified and characterized. Here, we demonstrate the biochemical and physiological characterization of a pyrophosphatase from Arabidopsis thaliana, called AtCoAse (locus tag At5g45940), cleaving CoA to 4'-phosphopantetheine and 3',5'-adenosine-diphosphate in the presence of Mg2+/Mn2+ ions. The CoA cleaving enzyme isa member of the Nudix hydrolases, pyrophosphatases that hydrolyze nucleoside diphosphates, already described as CoAse and now further characterized in detail by us. Mutagenesis of residues of the so-called Nudix and NuCoA motifs drastically reduced the hydrolase activity. AtCoAse is not absolute specific for CoA, and in the presence of Mn2+ ions, a minor hydrolyzing activity was observed with NADH as substrate. The AtCoAse expression is ubiquitous, strongly in flower and unaffected by abiotic stress. The immunohistochemical localization indicates that the AtCoAse protein is observed in the cytoplasm of distinct cells types from different heterotrophic Arabidopsis tissues, mainly restricted to the vascular elements of the root and shoot and in flower and developing embryo. Transgenic Arabidopsis plants, with increased AtCoAse expression, show altered growth rates and development, expanding their live cycle far away from the wild-type.