Molecular characterization of organelle-type Nudix hydrolases in Arabidopsis thaliana

Nudix (nucleoside diphosphates linked to some moiety X) hydrolases act to hydrolyze ribo-and deoxyribo-nucleoside triphophates, nucleotide sugars, coenzymes, or dinucleoside polyphosphates. Arabidopsis thaliana contains 27 genes encoding Nudix hydrolase homologues (AtNUDX1-27) with a predicted distribution in the cytosol, mitochondria, and chloroplasts. Previously, cytosolic Nudix hydrolases Here, we conducted a characterization of organelle-type AtNUDXs (AtNUDX12-24, 26, and 27). AtNUDX14 showed pyrophosphohydrolase activity toward both ADP-ribose and ADP-glucose, although its K m value was approx. 100-fold lower for ADP-ribose (K m : 13.0 ± 0.7 µM) than for ADP-glucose (1235 ± 65 µM). AtNUDX15 was hydrolyzed not only reduced CoA (118.7 ± 3.4 µM) but also a wide range of its derivatives. AtNUDX19 showed pyrophosphohydrolase activity toward both NADH (335.3 ± 5.4 µM) and NADPH (36.9 ± 3.5 µM). AtNUDX23 had FAD pyrophosphohydrolase activity (9.1 ± 0.9 µM). Both AtNUDX26 and AtNUDX27 hydrolyzed diadenosine polyphosphates (Ap n A; n=4-5). A confocal microscopic analysis using a GFP-fusion protein showed that AtNUDX15 is distributed in mitochondria and AtNUDX14 19, 23, 26, and 27 are in chloroplasts. These AtNUDX mRNAs were detected ubiquitously in various 25, 26, and 27 did not exhibit any phenotypical differences under normal growth conditions. The present results suggest that Nudix hydrolases in Arabidopsis control a variety of metabolites and are pertinent to a wide range of physiological processes.