title: Caenorhabditis elegans AGXT-1 is a mitochondrial and temperature-adapted ortholog of peroxisomal human AGT1: New insights into between-species divergence in glyoxylate metabolism.
abstract: In humans, glyoxylate is an intermediary product of metabolism, whose concentration is finely balanced. Mutations in peroxisomal alanine:glyoxylate aminotransferase (hAGT1) cause primary hyperoxaluria type 1 (PH1), which results in glyoxylate accumulation that is converted to toxic oxalate. In contrast, glyoxylate is used by the nematode Caenorhabditis elegans through a glyoxylate cycle to by-pass the decarboxylation steps of the tricarboxylic acid cycle and thus contributing to energy production and gluconeogenesis from stored lipids. To investigate the differences in glyoxylate metabolism between humans and C. elegans and to determine whether the nematode might be a suitable model for PH1, we have characterized here the predicted nematode ortholog of hAGT1 (AGXT-1) and compared its molecular properties with those of the human enzyme. Both enzymes form active PLP-dependent dimers with high specificity towards alanine and glyoxylate, and display similar three-dimensional structures. Interestingly, AGXT-1 shows 5-fold higher activity towards the alanine/glyoxylate pair than hAGT1. Thermal and chemical stability of AGXT-1 is lower than that of hAGT1, suggesting temperature-adaptation of the nematode enzyme linked to the lower optimal growth temperature of C. elegans. Remarkably, in vivo experiments demonstrate the mitochondrial localization of AGXT-1 in contrast to the peroxisomal compartmentalization of hAGT1. Our results support the view that the different glyoxylate metabolism in the nematode is associated with the divergent molecular properties and subcellular localization of the alanine:glyoxylate aminotransferase activity.
authors.affiliation: Department of Physical Chemistry, Faculty of Sciences, University of Granada, Av. Fuentenueva s/n, 18071 Granada, Spain. Electronic address: noelmesatorres@gmail.com.
authors.forename: Noel
authors.initials: N
authors.lastname: Mesa-Torres
authors.affiliation: Program in Cellular Neuroscience, Neurodegeneration, and Repair, Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06536, USA.
authors.forename: Ana C
authors.initials: AC
authors.lastname: Calvo
authors.affiliation: Department of Neurological, Biomedical and Movement Sciences, Section of Biological Chemistry, University of Verona, Strada Le Grazie 8, 37134 Verona, Italy.
authors.forename: Elisa
authors.initials: E
authors.lastname: Oppici
authors.affiliation: Department of Physical Chemistry, Faculty of Sciences, University of Granada, Av. Fuentenueva s/n, 18071 Granada, Spain; Program in Cellular Neuroscience, Neurodegeneration, and Repair, Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06536, USA.
authors.forename: Nicholas
authors.initials: N
authors.lastname: Titelbaum
authors.affiliation: Department of Neurological, Biomedical and Movement Sciences, Section of Biological Chemistry, University of Verona, Strada Le Grazie 8, 37134 Verona, Italy.
authors.forename: Riccardo
authors.initials: R
authors.lastname: Montioli
authors.affiliation: Instituto de Biomedicina de Sevilla, Hospital Universitario Virgen del Rocío/Consejo Superior de Investigaciones Científicas/Universidad de Sevilla, 41013 Sevilla, Spain.
authors.forename: Antonio
authors.initials: A
authors.lastname: Miranda-Vizuete
authors.affiliation: Department of Neurological, Biomedical and Movement Sciences, Section of Biological Chemistry, University of Verona, Strada Le Grazie 8, 37134 Verona, Italy.
authors.forename: Barbara
authors.initials: B
authors.lastname: Cellini
authors.affiliation: Centre for Biomedical Research on Rare Diseases (CIBERER), University Hospital of the Canary Islands, and CIBICAN, University of La Laguna, 38320 Tenerife, Spain.
authors.forename: Eduardo
authors.initials: E
authors.lastname: Salido
authors.affiliation: Department of Physical Chemistry, Faculty of Sciences, University of Granada, Av. Fuentenueva s/n, 18071 Granada, Spain. Electronic address: angelpey@ugr.es.
authors.forename: Angel L
authors.initials: AL
authors.lastname: Pey
mesh_terms: D000220:Adaptation, Biological; D000409:Alanine / Q000737:chemistry / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D005075:Biological Evolution; D017173:Caenorhabditis elegans / Q000235:genetics / Q000378:metabolism*; D029742:Caenorhabditis elegans Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D003001:Cloning, Molecular; D019281:Dimerization; D004734:Energy Metabolism; D004795:Enzyme Stability; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D006038:Glyoxylates / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D008928:Mitochondria / Q000378:metabolism*; D009154:Mutation; D020675:Peroxisomes / Q000378:metabolism*; D017433:Protein Structure, Secondary; D011732:Pyridoxal Phosphate / Q000737:chemistry / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D013045:Species Specificity; D040681:Structural Homology, Protein; D013696:Temperature; D000637:Transaminases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: D029742:Caenorhabditis elegans Proteins; D006038:Glyoxylates; D011994:Recombinant Proteins; D011732:Pyridoxal Phosphate; D000637:Transaminases; C019635:Alanine-glyoxylate transaminase; C031150:glyoxylic acid; D000409:Alanine
keywords: Conformational disease; Enzyme kinetics; Primary hyperoxaluria; Protein stability; Substrate specificity