title: GLYCOLATE OXIDASE3, a Glycolate Oxidase Homolog of Yeast l-Lactate Cytochrome c Oxidoreductase, Supports l-Lactate Oxidation in Roots of Arabidopsis.
abstract: In roots of Arabidopsis (Arabidopsis thaliana), l-lactate is generated by the reduction of pyruvate via l-lactate dehydrogenase, but this enzyme does not efficiently catalyze the reverse reaction. Here, we identify the Arabidopsis glycolate oxidase (GOX) paralogs GOX1, GOX2, and GOX3 as putative l-lactate-metabolizing enzymes based on their homology to CYB2, the l-lactate cytochrome c oxidoreductase from the yeast Saccharomyces cerevisiae. We found that GOX3 uses l-lactate with a similar efficiency to glycolate; in contrast, the photorespiratory isoforms GOX1 and GOX2, which share similar enzymatic properties, use glycolate with much higher efficiencies than l-lactate. The key factor making GOX3 more efficient with l-lactate than GOX1 and GOX2 is a 5- to 10-fold lower Km for the substrate. Consequently, only GOX3 can efficiently metabolize l-lactate at low intracellular concentrations. Isotope tracer experiments as well as substrate toxicity tests using GOX3 loss-of-function and overexpressor plants indicate that l-lactate is metabolized in vivo by GOX3. Moreover, GOX3 rescues the lethal growth phenotype of a yeast strain lacking CYB2, which cannot grow on l-lactate as a sole carbon source. GOX3 is predominantly present in roots and mature to aging leaves but is largely absent from young photosynthetic leaves, indicating that it plays a role predominantly in heterotrophic rather than autotrophic tissues, at least under standard growth conditions. In roots of plants grown under normoxic conditions, loss of function of GOX3 induces metabolic rearrangements that mirror wild-type responses under hypoxia. Thus, we identified GOX3 as the enzyme that metabolizes l-lactate to pyruvate in vivo and hypothesize that it may ensure the sustainment of low levels of l-lactate after its formation under normoxia.
authors.affiliation: Institute of Developmental and Molecular Biology of Plants, Plant Molecular Physiology and Biotechnology Group, Heinrich-Heine-Universität, and Cluster of Excellence on Plant Sciences, 40225 Duesseldorf, Germany (M.K.M.E., J.S., A.G., N.J., V.G.M.);Max-Planck-Institute of Molecular Plant Physiology, 14476 Potsdam-Golm, Germany (A.F., A.R.F.); andInstitute of Biochemistry and Biology, University of Potsdam, 14476 Potsdam, Germany (M.A., S.B., B.M.-R.).
authors.forename: Martin K M
authors.identifier: http://orcid.org/0000-0003-2174-2225
authors.initials: MK
authors.lastname: Engqvist
authors.affiliation: Institute of Developmental and Molecular Biology of Plants, Plant Molecular Physiology and Biotechnology Group, Heinrich-Heine-Universität, and Cluster of Excellence on Plant Sciences, 40225 Duesseldorf, Germany (M.K.M.E., J.S., A.G., N.J., V.G.M.);Max-Planck-Institute of Molecular Plant Physiology, 14476 Potsdam-Golm, Germany (A.F., A.R.F.); andInstitute of Biochemistry and Biology, University of Potsdam, 14476 Potsdam, Germany (M.A., S.B., B.M.-R.).
authors.forename: Jessica
authors.initials: J
authors.lastname: Schmitz
authors.affiliation: Institute of Developmental and Molecular Biology of Plants, Plant Molecular Physiology and Biotechnology Group, Heinrich-Heine-Universität, and Cluster of Excellence on Plant Sciences, 40225 Duesseldorf, Germany (M.K.M.E., J.S., A.G., N.J., V.G.M.);Max-Planck-Institute of Molecular Plant Physiology, 14476 Potsdam-Golm, Germany (A.F., A.R.F.); andInstitute of Biochemistry and Biology, University of Potsdam, 14476 Potsdam, Germany (M.A., S.B., B.M.-R.).
authors.forename: Anke
authors.initials: A
authors.lastname: Gertzmann
authors.affiliation: Institute of Developmental and Molecular Biology of Plants, Plant Molecular Physiology and Biotechnology Group, Heinrich-Heine-Universität, and Cluster of Excellence on Plant Sciences, 40225 Duesseldorf, Germany (M.K.M.E., J.S., A.G., N.J., V.G.M.);Max-Planck-Institute of Molecular Plant Physiology, 14476 Potsdam-Golm, Germany (A.F., A.R.F.); andInstitute of Biochemistry and Biology, University of Potsdam, 14476 Potsdam, Germany (M.A., S.B., B.M.-R.).
authors.forename: Alexandra
authors.initials: A
authors.lastname: Florian
authors.affiliation: Institute of Developmental and Molecular Biology of Plants, Plant Molecular Physiology and Biotechnology Group, Heinrich-Heine-Universität, and Cluster of Excellence on Plant Sciences, 40225 Duesseldorf, Germany (M.K.M.E., J.S., A.G., N.J., V.G.M.);Max-Planck-Institute of Molecular Plant Physiology, 14476 Potsdam-Golm, Germany (A.F., A.R.F.); andInstitute of Biochemistry and Biology, University of Potsdam, 14476 Potsdam, Germany (M.A., S.B., B.M.-R.).
authors.forename: Nils
authors.initials: N
authors.lastname: Jaspert
authors.affiliation: Institute of Developmental and Molecular Biology of Plants, Plant Molecular Physiology and Biotechnology Group, Heinrich-Heine-Universität, and Cluster of Excellence on Plant Sciences, 40225 Duesseldorf, Germany (M.K.M.E., J.S., A.G., N.J., V.G.M.);Max-Planck-Institute of Molecular Plant Physiology, 14476 Potsdam-Golm, Germany (A.F., A.R.F.); andInstitute of Biochemistry and Biology, University of Potsdam, 14476 Potsdam, Germany (M.A., S.B., B.M.-R.).
authors.forename: Muhammad
authors.identifier: http://orcid.org/0000-0002-2429-1899
authors.initials: M
authors.lastname: Arif
authors.affiliation: Institute of Developmental and Molecular Biology of Plants, Plant Molecular Physiology and Biotechnology Group, Heinrich-Heine-Universität, and Cluster of Excellence on Plant Sciences, 40225 Duesseldorf, Germany (M.K.M.E., J.S., A.G., N.J., V.G.M.);Max-Planck-Institute of Molecular Plant Physiology, 14476 Potsdam-Golm, Germany (A.F., A.R.F.); andInstitute of Biochemistry and Biology, University of Potsdam, 14476 Potsdam, Germany (M.A., S.B., B.M.-R.).
authors.forename: Salma
authors.identifier: http://orcid.org/0000-0002-5789-4071
authors.initials: S
authors.lastname: Balazadeh
authors.affiliation: Institute of Developmental and Molecular Biology of Plants, Plant Molecular Physiology and Biotechnology Group, Heinrich-Heine-Universität, and Cluster of Excellence on Plant Sciences, 40225 Duesseldorf, Germany (M.K.M.E., J.S., A.G., N.J., V.G.M.);Max-Planck-Institute of Molecular Plant Physiology, 14476 Potsdam-Golm, Germany (A.F., A.R.F.); andInstitute of Biochemistry and Biology, University of Potsdam, 14476 Potsdam, Germany (M.A., S.B., B.M.-R.).
authors.forename: Bernd
authors.identifier: http://orcid.org/0000-0002-1410-464X
authors.initials: B
authors.lastname: Mueller-Roeber
authors.affiliation: Institute of Developmental and Molecular Biology of Plants, Plant Molecular Physiology and Biotechnology Group, Heinrich-Heine-Universität, and Cluster of Excellence on Plant Sciences, 40225 Duesseldorf, Germany (M.K.M.E., J.S., A.G., N.J., V.G.M.);Max-Planck-Institute of Molecular Plant Physiology, 14476 Potsdam-Golm, Germany (A.F., A.R.F.); andInstitute of Biochemistry and Biology, University of Potsdam, 14476 Potsdam, Germany (M.A., S.B., B.M.-R.).
authors.forename: Alisdair R
authors.initials: AR
authors.lastname: Fernie
authors.affiliation: Institute of Developmental and Molecular Biology of Plants, Plant Molecular Physiology and Biotechnology Group, Heinrich-Heine-Universität, and Cluster of Excellence on Plant Sciences, 40225 Duesseldorf, Germany (M.K.M.E., J.S., A.G., N.J., V.G.M.);Max-Planck-Institute of Molecular Plant Physiology, 14476 Potsdam-Golm, Germany (A.F., A.R.F.); andInstitute of Biochemistry and Biology, University of Potsdam, 14476 Potsdam, Germany (M.A., S.B., B.M.-R.) veronica.maurino@uni-duesseldorf.de.
authors.forename: Veronica G
authors.identifier: http://orcid.org/0000-0002-3124-1451
authors.initials: VG
authors.lastname: Maurino
mesh_terms: D000429:Alcohol Oxidoreductases / Q000235:genetics / Q000378:metabolism*; D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D005816:Genetic Complementation Test; D006016:Glycolates / Q000378:metabolism; D042844:L-Lactate Dehydrogenase (Cytochrome) / Q000235:genetics / Q000378:metabolism; D019344:Lactic Acid / Q000378:metabolism*; D009154:Mutation; D010084:Oxidation-Reduction; D018517:Plant Roots / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity
chemical_list: D029681:Arabidopsis Proteins; D006016:Glycolates; C031149:glycolic acid; D019344:Lactic Acid; D000429:Alcohol Oxidoreductases; D042844:L-Lactate Dehydrogenase (Cytochrome); C578060:Gox1 protein, Arabidopsis; C578061:Gox3 protein, Arabidopsis; C020821:glycollate oxidase