title: A glutathione-independent glyoxalase of the DJ-1 superfamily plays an important role in managing metabolically generated methylglyoxal in Candida albicans.
abstract: Methylglyoxal is a cytotoxic reactive carbonyl compound produced by central metabolism. Dedicated glyoxalases convert methylglyoxal to d-lactate using multiple catalytic strategies. In this study, the DJ-1 superfamily member ORF 19.251/GLX3 from Candida albicans is shown to possess glyoxalase activity, making this the first demonstrated glutathione-independent glyoxalase in fungi. The crystal structure of Glx3p indicates that the protein is a monomer containing the catalytic triad Cys(136)-His(137)-Glu(168). Purified Glx3p has an in vitro methylglyoxalase activity (Km = 5.5 mM and kcat = 7.8 s(-1)) that is significantly greater than that of more distantly related members of the DJ-1 superfamily. A close Glx3p homolog from Saccharomyces cerevisiae (YDR533C/Hsp31) also has glyoxalase activity, suggesting that fungal members of the Hsp31 clade of the DJ-1 superfamily are all probable glutathione-independent glyoxalases. A homozygous glx3 null mutant in C. albicans strain SC5314 displays greater sensitivity to millimolar levels of exogenous methylglyoxal, elevated levels of intracellular methylglyoxal, and carbon source-dependent growth defects, especially when grown on glycerol. These phenotypic defects are complemented by restoration of the wild-type GLX3 locus. The growth defect of Glx3-deficient cells in glycerol is also partially complemented by added inorganic phosphate, which is not observed for wild-type or glucose-grown cells. Therefore, C. albicans Glx3 and its fungal homologs are physiologically relevant glutathione-independent glyoxalases that are not redundant with the previously characterized glutathione-dependent GLO1/GLO2 system. In addition to its role in detoxifying glyoxals, Glx3 and its close homologs may have other important roles in stress response.
authors.affiliation: From the School of Biological Sciences and.
authors.forename: Sahar
authors.initials: S
authors.lastname: Hasim
authors.forename: Nur Ahmad
authors.initials: NA
authors.lastname: Hussin
authors.forename: Fadhel
authors.initials: F
authors.lastname: Alomar
authors.forename: Keshore R
authors.initials: KR
authors.lastname: Bidasee
authors.forename: Kenneth W
authors.initials: KW
authors.lastname: Nickerson
authors.forename: Mark A
authors.initials: MA
authors.lastname: Wilson
mesh_terms: D000445:Aldehyde Oxidoreductases / Q000235:genetics / Q000378:metabolism*; D002176:Candida albicans / Q000201:enzymology* / Q000235:genetics; D003451:Cryoprotective Agents / Q000494:pharmacology; D056426:Genetic Loci / Q000502:physiology; D005990:Glycerol / Q000493:pharmacokinetics; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D011765:Pyruvaldehyde / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013312:Stress, Physiological / Q000187:drug effects / Q000502:physiology*
chemical_list: D003451:Cryoprotective Agents; D006360:Heat-Shock Proteins; D029701:Saccharomyces cerevisiae Proteins; D011765:Pyruvaldehyde; D000445:Aldehyde Oxidoreductases; C091855:glyoxalase III; C496117:HSP31 protein, S cerevisiae; D005990:Glycerol
keywords: Candida albicans; DJ-1; Glycolysis; Glyoxalase; Hsp31; Methylglyoxal; Structural Biology; X-ray Crystallography