title: Carboxylation of epoxides to beta-keto acids in cell extracts of Xanthobacter strain Py2.
abstract: A novel enzymatic reaction involved in the metabolism of aliphatic epoxides by Xanthobacter strain Py2 is described. Cell extracts catalyzed the CO2-dependent carboxylation of propylene oxide (epoxypropane) to form acetoacetate and beta-hydroxybutyrate. The time courses of acetoacetate and beta-hydroxybutyrate formaton indicate that acetoacetate is the primary product of propylene oxide carboxylation and that beta-hydroxybutyrate is a secondary product formed by the reduction of acetoacetate. Analogous C5 carboxylation products were identified with 1,2-epoxybutane as the substrate. In the absence of CO2, propylene oxide and 1,2-epoxybutane were isomerized to form acetone and methyl ethyl ketone, respectively, as dead-end products. The carboxylation of short-chain epoxides to beta-keto acids is proposed to serve as the physiological reaction for the metabolism of aliphatic epoxides in Xanthobacter strain Py2.
authors.affiliation: Department of Chemistry and Biochemistry, Utah State University, Logan 84322-0300, USA.
authors.forename: J R
authors.initials: JR
authors.lastname: Allen
authors.forename: S A
authors.initials: SA
authors.lastname: Ensign
mesh_terms: D020155:3-Hydroxybutyric Acid; D000090:Acetoacetates / Q000378:metabolism; D000096:Acetone / Q000378:metabolism; D002087:Butyrates / Q000378:metabolism*; D002245:Carbon Dioxide / Q000378:metabolism*; D004852:Epoxy Compounds / Q000378:metabolism*; D006088:Gram-Negative Aerobic Bacteria / Q000201:enzymology / Q000378:metabolism*; D006885:Hydroxybutyrates / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D010084:Oxidation-Reduction
chemical_list: D000090:Acetoacetates; D002087:Butyrates; D004852:Epoxy Compounds; D006885:Hydroxybutyrates; D000096:Acetone; D002245:Carbon Dioxide; C016635:acetoacetic acid; D020155:3-Hydroxybutyric Acid; C009068:propylene oxide