Showing papers on "Lactoylglutathione lyase published in 2004"

Role for glyoxalase I in Alzheimer's disease

Abstract: P301L mutant tau transgenic mice develop neurofibrillary tangles, a histopathologic hallmark of Alzheimer's disease and frontotemporal dementia (FTDP-17). To identify differentially expressed genes and to gain insight into pathogenic mechanisms, we performed a stringent analysis of the microarray dataset obtained with RNA from whole brains of P301L mutant mice and identified a single up-regulated gene, glyoxalase I. This enzyme plays a critical role in the detoxification of dicarbonyl compounds and thereby reduces the formation of advanced glycation end products. In situ hybridization analysis revealed expression of glyoxalase I in all brain areas analyzed, both in transgenic and control mice. However, levels of glyoxalase I protein were significantly elevated in P301L brains, as shown by Western blot analysis and immunohistochemistry. Moreover, a glyoxalase I-specific antiserum revealed many intensely stained flame-shaped neurons in Alzheimer's disease brain compared with brains from nondemented controls. In addition, we examined a single nucleotide polymorphism predicting a nonconservative amino acid substitution at position 111 (E111A) in ethnically independent populations. We identified significant and consistent deviations from Hardy-Weinberg equilibrium, which points to the presence of selection forces. The E111A single nucleotide polymorphism was not associated with the risk for Alzheimer's disease in the overall population. Together, our data demonstrate the potential of transcriptomics applied to animal models of human diseases. They suggest a previously unidentified role for glyoxalase I in neurodegenerative disease.

A trypanothione-dependent glyoxalase I with a prokaryotic ancestry in Leishmania major.

Abstract: Glyoxalase I forms part of the glyoxalase pathway that detoxifies reactive aldehydes such as methylglyoxal, using the spontaneously formed glutathione hemithioacetal as substrate. All known eukaryotic enzymes contain zinc as their metal cofactor, whereas the Escherichia coli glyoxalase I contains nickel. Database mining and sequence analysis identified putative glyoxalase I genes in the eukaryotic human parasites Leishmania major, Leishmania infantum, and Trypanosoma cruzi, with highest similarity to the cyanobacterial enzymes. Characterization of recombinant L. major glyoxalase I showed it to be unique among the eukaryotic enzymes in sharing the dependence of the E. coli enzyme on nickel. The parasite enzyme showed little activity with glutathione hemithioacetal substrates but was 200-fold more active with hemithioacetals formed from the unique trypanosomatid thiol trypanothione. L. major glyoxalase I also was insensitive to glutathione derivatives that are potent inhibitors of all other characterized glyoxalase I enzymes. This substrate specificity is distinct from that of the human enzyme and is reflected in the modification in the L. major sequence of a region of the human protein that interacts with the glycyl-carboxyl moiety of glutathione, a group that is conjugated to spermidine in trypanothione. This trypanothione-dependent glyoxalase I is therefore an attractive focus for additional biochemical and genetic investigation as a possible target for rational drug design.

Activity of the Yap1 transcription factor in Saccharomyces cerevisiae is modulated by methylglyoxal, a metabolite derived from glycolysis.

Abstract: Methylglyoxal (MG) is synthesized during glycolysis, although it inhibits cell growth in all types of organisms. Hence, it has long been asked why such a toxic metabolite is synthesized in vivo. Glyoxalase I is a major enzyme detoxifying MG. Here we show that the Yap1 transcription factor, which is critical for the oxidative-stress response in Saccharomyces cerevisiae, is constitutively concentrated in the nucleus and activates the expression of its target genes in a glyoxalase I-deficient mutant. Yap1 contains six cysteine residues in two cysteine-rich domains (CRDs), i.e., three cysteine residues clustering near the N terminus (n-CRD) and the remaining three cysteine residues near the C terminus (c-CRD). We reveal that any of the three cysteine residues in the c-CRD is sufficient for MG to allow Yap1 to translocate into the nucleus and to activate the expression of its target gene. A Yap1 mutant possessing only one cysteine residue in the c-CRD but no cysteine in the n-CRD and deletion of the basic leucine zipper domain can concentrate in the nucleus with MG treatment. However, substitution of all the cysteine residues in Yap1 abolishes the ability of this transcription factor to concentrate in the nucleus following MG treatment. The redox status of Yap1 is substantially unchanged, and protein(s) interaction with Yap1 through disulfide bond is hardly detected in cells treated with MG. Collectively, neither intermolecular nor intramolecular disulfide bond formation seems to be involved in Yap1 activation by MG. Moreover, we show that nucleocytoplasmic localization of Yap1 closely correlates with growth phase and intracellular MG level. We propose a novel regulatory pathway underlying Yap1 activation by a natural metabolite in the cell.

Glutathione analogues in cancer treatment.

Abstract: Glutathione is an important intracellular antioxidant and redox potential regulator that plays a vital role in drug detoxification and elimination and in cellular protection from damage by free radicals, peroxides, and toxins. Molecular alterations reported in many of the components of the glutathione system in various tumors and cancer cell lines can lead to increased survival and enhanced chemotherapy drug resistance. Several glutathione analogues that target this system have been developed and used experimentally and clinically in an attempt to improve cancer chemotherapy. These compounds include glutathione-S-transferase inhibitors and prodrugs, glyoxalase I inhibitors, and S-nitrosoglutathione. Work with these analogues has shown promising results, although lack of tumor specificity is a potential problem. Continuing development and optimization of glutathione analogues will lead to more specific targeting of this system in cancer treatment, allowing an increased therapeutic response.

Identification of thermostable glyoxalase I in the fission yeast Schizosaccharomyces pombe

Abstract: Glyoxalase I is a ubiquitous enzyme that detoxifies methylglyoxal, which is derived from glycolysis but inhibits the growth of cells from microorganisms to mammals. Here, the structural gene for glyoxalase I ( glo1(+)) from the fission yeast Schizosaccharomyces pombe was identified. Disruption of glo1(+) enhanced susceptibility to methylglyoxal, while expression of glo1(+) in a Delta glo1 mutant of Saccharomyces cerevisiae restored tolerance to this aldehyde. The glo1(+) gene product was purified. The glyoxalase I of S. pombe was a monomeric enzyme with a molecular weight of 34000 and the k(cat)/ K(m) value for methylglyoxal was 4.3 x 10(7) M(-1) x min(-1). Treatment of purified enzyme with EDTA in imidazole buffer completely abolished enzyme activity, whereas the EDTA-treated enzyme was reactivated by several divalent metal ions, such as Zn(2+), Co(2+), Ni(2+) and Mn(2+). The glyoxalase I of S. pombe exhibited fairly high thermal stability, and almost 100% activity was retained after incubating the enzyme at 60 degrees C for 4 h.

Methylglyoxal can completely replace the requirement of kinetin to induce differentiation of plantlets from some plant calluses

Abstract: It is well known that cytokinins, a group of plant hormones are absolutely required for the differentiation of calluses for the regeneration of plantlets through organogenesis. In the present work, it had been observed that methylglyoxal could completely replace kinetin to initiate differentiation of plantlets from calluses of Solanum nigrum and Daucus carota. Moreover, the effect of methylglyoxal was more pronounced compared to that of kinetin and the optimum concentration for methylglyoxal had been determined to be 0.5Â mM. Parallel with the differentiation of calluses to plantlets, the chlorophyll contents increased whereas the endogenous level of methylglyoxal remained unchanged. This remarkable effect of methylglyoxal in plant differentiation had been found out to be specific because some related compounds such as pyruvate and -lactate could not replace the requirement for methylglyoxal in the differentiation process. The activities of several enzymes were monitored during both methylglyoxal and kinetin-induced differentiation. The activity of the enzyme glyceraldehyde-3-phosphate dehydrogenase (NADP-dependent) involved in energy generation process in photosynthesis, increased as the differentiation proceeded. Whereas, the activities of both glucose-6-phosphate dehydrogenase and glyceraldehyde-3-phosphate dehydrogenase (NAD-dependent) decreased with differentiation. The activity of glyoxalase I, which catalyzes the conversion of methylglyoxal and glutathione to S--lactoylglutathione, decreased with differentiation. The endogenous level of glutathione showed an initial decrease followed by an increase. It appears from the results presented above, that the effect of kinetin and methylglyoxal are similar in nature, the significance of which has been discussed.

Role of rpoS in the regulation of glyoxalase III in Escherichia coli.

Abstract: Methylglyoxal is an endogenous electrophile produced in Escherichia coli by the enzyme methylglyoxal synthase to limit the accumulation of phosphorylated sugars. In enteric bacteria methylglyoxal is detoxified by the glutathione-dependent glyoxalase I/II system, by glyoxalase III, and by aldehyde reductase and alcohol dehydrogenase. Here we demonstrate that glyoxalase III is a stationary-phase enzyme. Its activity reached a maximum at the entry into the stationary phase and remained high for at least 20 h. An rpoS- mutant displayed normal glyoxalase I and II activities but was unable to induce glyoxalase III in stationary phase. It thus appears that glyoxalase III is regulated by rpoS and might be important for survival of non-growing E. coli cultures.

Functional characterisation of glyoxalase I from the fungal wheat pathogen Stagonospora nodorum.

Abstract: During an expressed sequence tag sequencing project, a gene encoding a methylglyoxal lyase (glyoxalase I) was identified, cloned and characterised from the necrotrophic wheat pathogen Stagonospora nodorum. Sequence analysis identified the gene, named Gox1, as having reasonable identity to GLO1 from yeast and hypothetical proteins identified in fungal genome sequencing projects. Expression analysis in vitro revealed Gox1 to be up-regulated in the presence of methylglyoxal and salt but not affected by starvation conditions. Analysis of Gox1 transcription in planta showed its highest expression was in ungerminated spores and during sporulation, suggesting a role for the glycolytic bypass pathway in sporulation. The gene was inactivated by homologous recombination, resulting in a S. nodorum strain with no detectable glyoxalase I activity. The gox1 mutants exhibited no discernable phenotype, with the exception of being more sensitive to the presence of methylglyoxal. Infection assays demonstrated the mutants retained full pathogenicity and sporulation was unaffected. This is the first report describing the characterisation of a glyoxalase I from a pathogen of any description. The gene has been sequenced, functionally characterised and shown not to be required for the infection of wheat by S. nodorum.