An Arabidopsis Oxalyl-CoA Decarboxylase, AtOXC, Is Important for Oxalate Catabolism in Plants

Authors

Justin Foster
Ninghui Cheng
Vincent Paris
Lingfei Wang
Jin Wang
Xiaoqiang Wang
Paul A Nakata

Publication Date

3-23-2021

Journal

International Journal of Molecular Sciences

DOI

10.3390/ijms22063266

PMID

33806862

PMCID

PMC8004701

PubMedCentral® Posted Date

3-23-2021

PubMedCentral® Full Text Version

Post-print

Published Open-Access

yes

Keywords

Amino Acid Sequence, Arabidopsis, Carboxy-Lyases, Chromatography, High Pressure Liquid, Cloning, Molecular, Enzyme Activation, Gene Expression Regulation, Plant, Metabolic Networks and Pathways, Models, Molecular, Oxalates, Oxidation-Reduction, Plant Development, Plant Physiological Phenomena, Protein Conformation, Protein Transport, oxalate, catabolism, decarboxylase

Abstract

Considering the widespread occurrence of oxalate in nature and its broad impact on a host of organisms, it is surprising that so little is known about the turnover of this important acid. In plants, oxalate oxidase is the most well-studied enzyme capable of degrading oxalate, but not all plants possess this activity. Recently, acyl-activating enzyme 3 (AAE3), encoding an oxalyl-CoA synthetase, was identified in Arabidopsis. This enzyme has been proposed to catalyze the first step in an alternative pathway of oxalate degradation. Since this initial discovery, this enzyme and proposed pathway have been found to be important to other plants and yeast as well. In this study, we identify, in Arabidopsis, an oxalyl-CoA decarboxylase (AtOXC) that is capable of catalyzing the second step in this proposed pathway of oxalate catabolism. This enzyme breaks down oxalyl-CoA, the product of AtAAE3, into formyl-CoA and CO2. AtOXC:GFP localization suggested that this enzyme functions within the cytosol of the cell. An Atoxc knock-down mutant showed a reduction in the ability to degrade oxalate into CO2. This reduction in AtOXC activity resulted in an increase in the accumulation of oxalate and the enzyme substrate, oxalyl-CoA. Size exclusion studies suggest that the enzyme functions as a dimer. Computer modeling of the AtOXC enzyme structure identified amino acids of predicted importance in co-factor binding and catalysis. Overall, these results suggest that AtOXC catalyzes the second step in this alternative pathway of oxalate catabolism.