Short-chain acyl-CoA-dependent production of oxalate from oxaloacetate by Burkholderia glumae, a plant pathogen which causes grain rot and seedling rot of rice via the oxalate production.

Abstract

In Burkholderia glumae (formerly named Pseudomonas glumae), isolated as the causal agent of grain rot and seedling rot of rice, oxalate was produced from oxaloacetate in the presence of short-chain acyl-CoA such as acetyl-CoA and propionyl-CoA. Upon purification, the enzyme responsible was separated into two fractions (tentatively named fractions II and III), both of which were required for the acyl-CoA-dependent production of oxalate. In conjugation with the oxalate production from oxaloacetate catalyzed by fractions II and III, acetyl-CoA used as the acyl-CoA substrate was consumed and equivalent amounts of CoASH and acetoacetate were formed. The isotope incorporation pattern indicated that the two carbon atoms of oxalate are both derived from oxaloacetate, and among the four carbon atoms of acetoacetate two are from oxaloacetate and two from acetyl-CoA. When the reaction was carried out with fraction II alone, a decrease in acetyl-CoA and an equivalent level of net utilization of oxaloacetate were observed without appreciable formation of CoASH, acetoacetate or oxalate. It appears that in the oxalate production from oxaloacetate and acetyl-CoA, fraction II catalyzes condensation of the two substrates to form an intermediate which is split into oxalate and acetoacetate by fraction III being accompanied by the release of CoASH.