Location: Children's Nutrition Research CenterTitle: Characterization of oryza sativa acyl activating enzyme3 (OsAAE3)
|LAMBERT, PETER - CHILDREN'S NUTRITION RESEARCH CENTER (CNRC)|
Submitted to: Plant Biology Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 6/1/2015
Publication Date: 7/25/2015
Citation: Lambert, P.M., Nakata, P.A. 2015. Characterization of oryza sativa acyl activating enzyme3 (OsAAE3). Plant Biology Annual Meeting. Plant Biology 2015. July 25-30, 2015, Minneapolis, MN.
Technical Abstract: Oxalate, the smallest of the dicarboxylic acids, is produced in many plants. This acid has been shown to play an important role in both plant physiology and defense, specifically in regards to metal detoxification, calcium regulation, sucking and chewing insect deterrence, and the production of calcium oxalate crystals. The most studied pathway in plants for oxalic acid degradation involves an oxalate oxidase that converts oxalic acid to CO2 and H2O2. This activity has been detected extensively in monocots, including wheat, barley, and rice. Recently, a novel pathway of oxalate metabolism was proposed in Arabidopsis, a plant that lacks oxalate oxidase activity. Acyl activating enzyme (AAE) 3, encoding an oxalyl-CoA synthetase, was proposed to catalyze the first step in this novel pathway of oxalate catabolism. The discovery of AtAAE3 has sparked a search for homologous pathways in other plants including crop plants. This study identifies Oryza sativa ACYL-ACTIVATING ENZYME3 (OsAAE3: Os04g0683700) as a gene encoding an oxalyl-CoA synthetase. This activity is particularly interesting given that rice also possesses the more common oxalate catabolic pathway utilizing oxalate oxidases. To investigate the function of OsAAE3 we have produced a recombinant enzyme that demonstrates activity against oxalate in vitro, exhibiting Michaelis-Menten kinetics with a Km of 98.24 +/- 19.94 uM and a Vmax of 6.880 +/- 0.3218 umol/min/mg. Additionally, we have introduced OsAAE3 into Ataae3 null mutants, and found that plants expressing OsAAE3 in the mutant background have a lower concentration of tissue oxalate than the Ataae3 null mutants. This decrease in oxalate is accompanied by a reduction in calcium oxalate crystals seen in the OsAAE3 plants.