transulfuration glutathione

1: Eukaryot Cell. 2006 Oct;5(10):1748-59. Epub 2006 Aug 25. Related Articles, Links
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A Peroxisomal Glutathione Transferase of Saccharomyces cerevisiae Is Functionally Related to Sulfur Amino Acid Metabolism.

Barreto L, Garcera A, Jansson K, Sunnerhagen P, Herrero E.

Departament de Ciencies Mediques Basiques, Facultat de Medicina, Universitat de Lleida, Montserrat Roig 2, 25008 Lleida, Spain.

Saccharomyces cerevisiae cells contain three omega-class glutathione transferases with glutaredoxin activity (Gto1, Gto2, and Gto3), in addition to two glutathione transferases (Gtt1 and Gtt2) not classifiable into standard classes. Gto1 is located at the peroxisomes, where it is targeted through a PTS1-type sequence, whereas Gto2 and Gto3 are in the cytosol. Among the GTO genes, GTO2 shows the strongest induction of expression by agents such as diamide, 1-chloro-2,4-dinitrobenzene, tert-butyl hydroperoxide or cadmium, in a manner that is dependent on transcriptional factors Yap1 and/or Msn2/4. Diamide and 1-chloro-2,4-dinitrobenzene (causing depletion of reduced glutathione) also induce expression of GTO1 over basal levels. Phenotypic analyses with single and multiple mutants in the S. cerevisiae glutathione transferase genes show that, in the absence of Gto1 and the two Gtt proteins, cells display increased sensitivity to cadmium. A gto1-null mutant also shows growth defects on oleic acid-based medium, which is indicative of abnormal peroxisomal functions, and altered expression of genes related to sulfur amino acid metabolism. As a consequence, growth of the gto1 mutant is delayed in growth medium without lysine, serine, or threonine, and the mutant cells have low levels of reduced glutathione. The role of Gto1 at the S. cerevisiae peroxisomes could be related to the redox regulation of the Str3 cystathionine beta-lyase protein. This protein is also located at the peroxisomes in S. cerevisiae, where it is involved in transulfuration of cysteine into homocysteine, and requires a conserved cysteine residue for its biological activity.

PMID: 16936141 [PubMed – in process]

2: Biomarkers. 2006 Jan-Feb;11(1):53-60. Related Articles, Links
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MTHFR C677T polymorphism, GSTM1 deletion and male infertility: a possible suggestion of a gene-gene interaction?

Paracchini V, Garte S, Taioli E.

University of Pittsburgh Cancer Institute, Pittsburgh, PA 15232, USA.

Methylenetetrahydrofolate reductase (MTHFR) is a gene involved in the process of DNA synthesis and methylation. The MTHFR C677T polymorphism has been associated with male infertility. A prospective study was conducted on men seeking care at the infertility clinic in Milano to determine if the MTHFR C677T polymorphism is associated with infertility, and if such an association is modified by a common deletion of one of the glutathione transferases, GSTM1. One year after enrolment, 46 subjects reported having had a child, while 59 were still childless. Subjects carrying the MTHFR C677T homozygous variant polymorphism were at increased risk of being infertile after 1-year follow-up (OR 3.7, 95% CI?=?1.4-10.4); carriers of the homozygous variant MTHFR genotype and of a functional copy of GSTM1 appear to have a significantly higher risk of infertility (n=11; OR?=?22.0 95% CI?=?3.8-127.9) than subjects who carry the wild-type genotype for both genes. Such risk becomes non-significant when the GSTM1 deletion is also present (n=5; OR?=?1.1 95% CI?=?0.2-5.1). A possible explanation of this unexpected result could lie in the known involvement of glutathione transferases in the metabolic pathways of both methylation and transulfuration. The interaction found deserves confirmation and replication in a larger population, since it may be relevant to several chronic diseases such as cardiovascular diseases and cancer.

PMID: 16484136 [PubMed – indexed for MEDLINE]

3: J Nutr Biochem. 1999 Aug;10(8):490-7. Related Articles, Links
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A new HPLC method for the simultaneous determination of oxidized and reduced plasma aminothiols using coulometric electrochemical detection.

Melnyk S, Pogribna M, Pogribny I, Hine RJ, James SJ.

Division of Biochemical Toxicology, FDA-National Center for Toxicological Research, Jefferson, AR 72079, USA.

A new method has been developed that is capable of providing a complete profile of the most common monothiols and disulfides present in plasma or tissue extracts. The method utilizes reversed phase ion-pairing high performance liquid chromatography coupled with coulometric electrochemical detection to simultaneously quantify free oxidized and reduced aminothiols or total aminothiols after chemical reduction. The method is extremely sensitive, with limits of detection in the 5 fmol/mL range for monothiols and 50 fmol/mL for dithiols. The interassay and intraassay coefficients of variation for total and free aminothiols ranged between 1.2 and 5.8%. The mean recoveries for total and plasma aminothiols ranged between 97.1 and 102.8%. The aminothiols are quantified directly, without derivatization, and include methionine, homocysteine, homocystine, cystathionine, cysteine, cystine, cysteinylglycine, and oxidized and reduced glutathione. Because a complete aminothiol profile of metabolites in both the remethylation (anabolic) and transulfuration (catabolic) pathways of homocysteine metabolism can be determined simultaneously, this new method should be useful in determining the metabolic etiology of homocysteinemia and in designing appropriate nutritional intervention strategies. Basic research applications of this method should lead to an increased understanding of the metabolic pathology of aminothiol imbalance.

PMID: 15539328 [PubMed]

4: J Biol Chem. 1988 Nov 25;263(33):17262-9. Related Articles, Links
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Persulfide generated from L-cysteine inactivates tyrosine aminotransferase. Requirement for a protein with cysteine oxidase activity and gamma-cystathionase.

Hargrove JL.

Department of Anatomy and Cell Biology, Emory University School of Medicine, Atlanta, Georgia 30322.

Liver cytosols contain factors that produce an inhibitor of tyrosine aminotransferase and other enzymes when incubated with L-cysteine or L-cystine. Cystine-dependent inactivation was caused by cystathionase and required pyridoxal 5′-phosphate, but a second protein was needed to reconstitute cysteine-dependent inactivation. A cytosolic protein was isolated that oxidized free cysteine and brought about inactivation of tyrosine aminotransferase when coincubated with cystathionase. Hematin also oxidized cysteine, which led to cysteine-dependent inactivation of tyrosine aminotransferase in the presence of cystathionase. The inactivation of tyrosine aminotransferase involved three steps: initial oxidation of cysteine to form cystine; desulfuration of cystine catalyzed by cystathionase to form the persulfide, thiocysteine; and reaction of thiocysteine (or products of its decomposition) with proteins to form protein-bound sulfane. Since dithiothreitol reactivated tyrosine aminotransferase, the sulfane probably inactivated the enzyme by oxidation of thiol groups. The present results do not indicate whether the cysteine oxidase activity is enzymatic nor do they prove which form of polysulfide inactivates tyrosine aminotransferase. Reduced glutathione greatly slowed the rates at which sulfane accumulated and at which tyrosine aminotransferase was inactivated. Incubation of DL-cystathionine with liver cytosols led to formation of cysteine, which was oxidized and cleaved to form persulfide, and caused inactivation of tyrosine aminotransferase. Thus, sulfane sulfur that is generated by an enzyme of the transulfuration pathway inactivates a transaminase by nonselective oxidation of enzyme-bound thiol groups.

PMID: 2903161 [PubMed – indexed for MEDLINE]


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