A conserved oxalyl-Coenzyme A decarboxylase in oxalate catabolism

Authors: CHENG, NINGHUI - Children'S Nutrition Research Center (CNRC); PARIS, VINCENT - University Of North Texas; RAO, XIAOLAN - Hubei University; WANG, XIAOQIANG - University Of North Texas; Nakata, Paul

Submitted to: Plant Signaling and Behavior
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/1/2022
Publication Date: 5/5/2022
Citation: Cheng, N., Paris, V., Rao, X., Wang, X., Nakata, P.A. 2022. A conserved oxalyl-coenzyme A decarboxylase in oxalate catabolism. Plant Signaling and Behavior. 17:1. https://doi.org/10.1080/15592324.2022.2062555.
DOI: https://doi.org/10.1080/15592324.2022.2062555

Interpretive Summary: With an increasing human population and decreasing areas for crop production there is a need to improve our ability to produce nutritious food. Thus, plant scientists have been seeking new strategies to improve the nutritional quality of plant foods. Oxalate present in plant foods often lowers the nutritional value of foods by binding to calcium to form an insoluble crystal that prevents the absorption of the bound calcium. In addition, soluble oxalate can be absorbed directly from the diet, primarily from plant based foods, and contribute to the formation of kidney stones. A potential strategy to decrease oxalate in plant foods is to exploit the natural oxalate degradation pathways that already exist in the plant. In this study we report on the enzyme, oxalyl-CoA decarboxylase, which catalyzes the second step in a previously uncharacterized pathway of oxalate degradation. Data analysis indicated that this enzyme is conserved across plant species and that the way in which this enzyme functions is the same in different plants. Expression analysis showed that the gene which encodes this enzyme was regulated by oxalate in the different plants. Knowledge about this enzyme as well as the other enzymes that make up this pathway of oxalate degradation would help efforts to improve the nutritional quality of plant foods.

Technical Abstract: The ability to biosynthesize oxalic acid provides beneficial functions to plants; however, uncontrolled or prolonged exposure to this strong organic acid results in multiple physiological problems. Such problems include a disruption of membrane integrity, mitochondrial function, metal chelation, and free radical formation. Recent work suggests that a CoA-dependent pathway of oxalate catabolism plays a critical role in regulating tissue oxalate concentrations in plants. Although this CoA-dependent pathway of oxalate catabolism is important, large gaps in our knowledge of the enzymes catalyzing each step remain. Evidence that an oxalyl-CoA decarboxylase (OXC) catalyzes the second step in this pathway, accelerating the conversion of oxalyl-CoA to formyl-CoA, has been reported. Induction studies revealed that OXC gene expression was upregulated in response to an exogenous oxalate supply. Phylogenetic analysis indicates that OXCs are conserved across plant species. Evolutionarily the plant OXCs can be separated into dicot and monocot classes. Multiple sequence alignments and molecular modeling suggest that OXCs have similar functionality with three conserved domains, the N-terminal PYR domain, the middle R domain, and the C-terminal PP domain. Further study of this CoA-dependent pathway of oxalate degradation would benefit efforts to develop new strategies to improve the nutrition quality of crops.