title: The oxidative fermentation of ethanol in Gluconacetobacter diazotrophicus is a two-step pathway catalyzed by a single enzyme: alcohol-aldehyde Dehydrogenase (ADHa).
abstract: Gluconacetobacter diazotrophicus is a N2-fixing bacterium endophyte from sugar cane. The oxidation of ethanol to acetic acid of this organism takes place in the periplasmic space, and this reaction is catalyzed by two membrane-bound enzymes complexes: the alcohol dehydrogenase (ADH) and the aldehyde dehydrogenase (ALDH). We present strong evidence showing that the well-known membrane-bound Alcohol dehydrogenase (ADHa) of Ga. diazotrophicus is indeed a double function enzyme, which is able to use primary alcohols (C2-C6) and its respective aldehydes as alternate substrates. Moreover, the enzyme utilizes ethanol as a substrate in a reaction mechanism where this is subjected to a two-step oxidation process to produce acetic acid without releasing the acetaldehyde intermediary to the media. Moreover, we propose a mechanism that, under physiological conditions, might permit a massive conversion of ethanol to acetic acid, as usually occurs in the acetic acid bacteria, but without the transient accumulation of the highly toxic acetaldehyde.
authors.affiliation: Laboratorio de Bioquímica-Genética, Instituto Nacional de Pediatría, S.S. Mexico City 04530, Mexico. saulmanzo@ciencias.unam.mx.
authors.forename: Saúl
authors.initials: S
authors.lastname: Gómez-Manzo
authors.affiliation: Departamento de Bioquímica y Biología Estructural, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City 04510, Mexico. mcontre@ifc.unam.mx.
authors.forename: José E
authors.initials: JE
authors.lastname: Escamilla
authors.affiliation: Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Mexico City 04510, Mexico. abigaila@correo.biomedicas.unam.mx.
authors.forename: Abigail
authors.initials: A
authors.lastname: González-Valdez
authors.affiliation: Laboratorio de Bioquímica-Genética, Instituto Nacional de Pediatría, S.S. Mexico City 04530, Mexico. glv_1999@yahoo.com.
authors.forename: Gabriel
authors.initials: G
authors.lastname: López-Velázquez
authors.affiliation: Laboratorio de Bioquímica-Genética, Instituto Nacional de Pediatría, S.S. Mexico City 04530, Mexico. america_vc@yahoo.com.mx.
authors.forename: América
authors.initials: A
authors.lastname: Vanoye-Carlo
authors.affiliation: CONACyT, Comisionado a Instituto Nacional de Pediatría, S.S. Mexico City 03940, Mexico. jmarcialqu@conacyt.mx.
authors.forename: Jaime
authors.initials: J
authors.lastname: Marcial-Quino
authors.affiliation: Laboratorio de Bioquímica-Genética, Instituto Nacional de Pediatría, S.S. Mexico City 04530, Mexico. ignaciodelamora@yahoo.com.mx.
authors.forename: Ignacio
authors.initials: I
authors.lastname: de la Mora-de la Mora
authors.affiliation: Laboratorio de Bioquímica-Genética, Instituto Nacional de Pediatría, S.S. Mexico City 04530, Mexico. itzheltorres@hotmail.com.
authors.forename: Itzhel
authors.initials: I
authors.lastname: Garcia-Torres
authors.affiliation: Laboratorio de Bioquímica-Genética, Instituto Nacional de Pediatría, S.S. Mexico City 04530, Mexico. sergioenr@gmail.com.
authors.forename: Sergio
authors.initials: S
authors.lastname: Enríquez-Flores
authors.affiliation: Departamento de Bioquímica y Biología Estructural, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City 04510, Mexico. mcontre@ifc.unam.mx.
authors.forename: Martha Lucinda
authors.initials: ML
authors.lastname: Contreras-Zentella
authors.affiliation: Departamento de Química de Biomacromoléculas, Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior s/n, Ciudad Universitaria, Mexico City 04510, Mexico. arrespin@unam.mx.
authors.forename: Roberto
authors.initials: R
authors.lastname: Arreguín-Espinosa
authors.affiliation: Fachbereich Biologie, Universität Konstanz, 78457 Konstanz, Germany. Peter.Kroneck@Uni-Konstanz.de.
authors.forename: Peter M H
authors.initials: PM
authors.lastname: Kroneck
authors.affiliation: Departamento de Química Inorgánica y Nuclear, Facultad de Química, Universidad Nacional Autónoma de México, Mexico City 04510, Mexico. mest@unam.mx.
authors.forename: Martha Elena
authors.initials: ME
authors.lastname: Sosa-Torres
mesh_terms: D000085:Acetates / Q000032:analysis; D000426:Alcohol Dehydrogenase / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D000447:Aldehydes / Q000032:analysis; D000595:Amino Acid Sequence; D055162:Biocatalysis; D002250:Carbon Radioisotopes / Q000737:chemistry; D000431:Ethanol / Q000378:metabolism*; D008401:Gas Chromatography-Mass Spectrometry; D041821:Gluconacetobacter / Q000201:enzymology*; D007553:Isotope Labeling; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D011489:Protein Denaturation; D013696:Temperature
chemical_list: D000085:Acetates; D000447:Aldehydes; D002250:Carbon Radioisotopes; D000431:Ethanol; D000426:Alcohol Dehydrogenase