Journal Article

Cloning, Expression and Characterization of a Nudix Hydrolase that Catalyzes the Hydrolytic Breakdown of ADP-glucose Linked to Starch Biosynthesis in <i>Arabidopsis thaliana</i>

Francisco José Muñoz, Edurne Baroja-Fernández, María Teresa Morán-Zorzano, Nora Alonso-Casajús and Javier Pozueta-Romero

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 47, issue 7, pages 926-934
Published in print July 2006 | ISSN: 0032-0781
Published online July 2006 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcj065
Cloning, Expression and Characterization of a Nudix Hydrolase that Catalyzes the Hydrolytic Breakdown of ADP-glucose Linked to Starch Biosynthesis in Arabidopsis thaliana

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  • Biochemistry
  • Molecular and Cell Biology
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‘Nudix’ hydrolases are widely distributed nucleotide pyrophosphatases that possess a conserved GX5EX7REUXEEXGU motif where U is usually isoleucine, leucine or valine. Among them, Escherichia coli ADP-sugar pyrophosphatase (ASPP) has been shown to catalyze the hydrolytic breakdown of ADP-glucose linked to bacterial glycogen biosynthesis. Comparisons of the 31 different Nudix-encoding sequences of the Arabidopsis genome with those coding for known bacterial and mammalian ASPPs identified one sequence possessing important divergences in the Nudix motif that, once expressed in E. coli, produced a protein with ASPP activity. This protein, designated as AtASPP, shares strong homology with hypothetical rice and potato proteins, indicating that ASPPs are widely distributed in both mono- and dicotyledonous plants. As a first step to test the possible involvement of plant ASPPs in regulating the intracellular levels of ADP-glucose linked to starch biosynthesis, we produced and characterized AtASPP-overexpressing Arabidopsis plants. Source leaves from these plants exhibited a large reduction in the levels of both ADP-glucose and starch, indicating that plant ASPPs catalyze the hydrolytic breakdown of a sizable pool of ADP-glucose linked to starch biosynthesis. No pleiotropic changes in maximum catalytic activities of enzymes closely linked to starch metabolism could be detected in AtASPP-overexpressing leaves. The overall information provides the first evidence for the existence of plant Nudix hydrolases that have access to an intracellular pool of ADP-glucose linked to starch biosynthesis.

Keywords: Arabidopsis thaliana; Carbohydrate metabolism; Nudix hydrolase; Solanum tuberosum; Starch

Journal Article.  4646 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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