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  • 1
    Electronic Resource
    Electronic Resource
    Metabolism ofl-cysteine via transamination pathway (3-mercaptopyruvate pathway) (1992)
    Springer
    Amino acids 3 (1992), S. 243-252 
    Details
    ISSN: 1438-2199
    Keywords: Amino acids ; Cysteine metabolism ; 3-Mercaptopyruvate pathway ; Cysteine transamination ; 3-Mercaptolactate-cysteine mixed disulfide ; Sulfate formation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We have studied the transamination pathway (3-mercaptopyruvate pathway) ofl-cysteine metabolism in rats. Characterization of cysteine aminotransferase (EC 2.6.1.3) from liver indicated that the transamination, the first reaction of this pathway, was catalyzed by aspartate aminotransferase (EC 2.6.1.1). 3-Mercaptopyruvate, the product of the transamination, may be metabolized through two routes. The initial reactions of these routes are reduction and transsulfuration, and the final metabolites are 3-mercaptolactate-cysteine mixed disulfide [S-(2-hydroxy-2-carboxyethylthio)cysteine, HCETC] and inorganic sulfate, respectively. The study using anti-lactate dehydrogenase antiserum proved that the enzyme catalyzing the reduction of 3-mercaptopyruvate was lactate dehydrogenase (EC 1.1.1.27). Formation of HCETC was shown to depend on low 3-mercaptopyruvate sulfurtransferase (EC 2.8.1.2) activity. Results were discussed in relation to HCETC excretion in normal human subjects and patients with 3-mercaptolactate-cysteine disulfiduria. Incubation of liver mitochondria withl-cysteine, 2-oxoglutarate and glutathione resulted in the formation of sulfate and thiosulfate, indicating that thiosulfate was formed by transsulfuration of 3-mercaptopyruvate and finally metabolized to sulfate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00805999
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  • 2
    Electronic Resource
    Electronic Resource
    Identification ofS-[2-carboxy-1-(1H-imidazol-4-yl)ethyl]-3-mercaptopyruvic acid with a metabolic intermediate betweenS-[2-carboxy-1-(1H-imidazol-4-yl)ethyl]-l-cysteine andS-[2-carboxy-1-(1H-imidazol-4-yl)ethyl]-3-mercaptolactic acid (1997)
    Springer
    Amino acids 13 (1997), S. 163-169 
    Details
    ISSN: 1438-2199
    Keywords: Amino acids ; Imidazole compound ; Mercaptopyruvic acid ; Urocanic acid ; Histidine ; Mass spectrometry ; Paper electrophoresis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary S-[2-Carboxy-1-(1H-imidazol-4-yl)ethyl]-3-mercaptopyruvic acid (I) was chemically synthesized in 15% yield by incubating a reaction mixture oftrans-urocanic acid and 3-fold excess of 3-mercaptopyruvic acid at 45°C for 6 days. The synthesized compound was characterized by fast-atom-bombardment mass spectrometry and high-voltage paper electrophoresis. CompoundI was identified with a product of an enzymatic reaction ofS-[2-carboxy-1-(1H-imidazol-4-yl)ethyl]-l-cysteine (II) with rat liver homogenate in a phosphate buffer, pH 7.4. CompoundI was degraded toS-[2-carboxy-1-(1H-imidazol-4-yl)ethyl]-3-mercaptolactic acid (III), a compound previously found in human urine [Kinuta et al. (1994) Biochem J 297: 475–478], by incubation with rat liver homogenate. From these results, we suggest that compoundI is a metabolic intermediate for the formation of compoundIII from compoundII. The present pathway follows a formation of compoundII fromS-[2-carboxy-1-(1H-imidazol-4-yl)ethyl] gluthathione [Kinuta et al. (1993) Biochim Biophys Acta 1157: 192–198], a proposed metabolite ofl-histidine.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01373214
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  • 3
    Electronic Resource
    Electronic Resource
    Effect ofN-acetylcysteine administration on cysteine and glutathione contents in liver and kidney and in perfused liver of intact and diethyl maleate-treated rats (1994)
    Springer
    Amino acids 7 (1994), S. 255-266 
    Details
    ISSN: 1438-2199
    Keywords: Amino acids ; N-Acetylcysteine ; Cysteine ; Glutathione ; Diethyl maleate ; Perfused rat liver
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Effect ofN-acetyl-l-cysteine (NAC) administration on cysteine and glutathione (GSH) contents in rat liver and kidney was studied using intact and diethyl maleate (DEM)-treated rats and perfused rat liver. Cysteine contents increased rapidly, reaching peak at 10 min after intraperitoneal NAC administration. In liver mitochondria it increased slowly, reaching peak at 60 min. GSH content did not change significantly in these tissues. However, in liver and kidney depleted of GSH with DEM, NAC administration restored GSH contents in 60 and 120 min, respectively. Perfusion with 10 mM NAC resulted in 76% increase in liver cysteine content, but not in GSH content. Liver perfusion of DEM-injected rats with 10 mM NAC restored GSH content by 15%. Present findings indicate that NAC is an effective precursor of cysteine in the intact liver and kidney and in the perfused rat liver, and that NAC stimulated GSH synthesis in GSH-depleted tissues.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00807701
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  • 4
    Electronic Resource
    Electronic Resource
    Inhibition of sulfate-forming activity in rat liver mitochondria by (aminooxy)acetate (1993)
    Springer
    Amino acids 5 (1993), S. 245-251 
    Details
    ISSN: 1438-2199
    Keywords: Amino acids ; Cysteine metabolism ; MP pathway ; Sulfate formation ; (Aminooxy)acetate ; Rat liver mitochondria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effect of (aminooxy)acetate, an inhibitor of aminotransferases, on the sulfate formation froml-cysteine andl-cysteinesulfinate in rat liver mitochondria was studied. Incubation of 10 mMl-cysteine with rat liver mitochondria at 37°C in the presence of 10 mM 2-oxoglutarate and 10 mM glutathione resulted in the formation of 4.60 and 1.52µmol of sulfate and thiosulfate, respectively, per 60 min per mitochondria obtained from 1 g of liver. Under the same conditions sulfate formation froml-cysteinesulfinate was 24.96µmol, but thiosulfate was not formed. The addition of (aminooxy)acetate at 2 mM or more completely inhibited the sulfate and thiosulfate formation froml-cysteine and the sulfate formation froml-cysteinesulfinate. These findings support our previous conclusion that cysteine transamination and 3-mercaptopyruvate pathway (MP pathway) are involved in the sulfate formation froml-cysteine in rat liver mitochondria (Ubuka et al., 1992).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00805987
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  • 5
    Electronic Resource
    Electronic Resource
    l-Cysteine metabolism via 3-mercaptopyruvate pathway and sulfate formation in rat liver mitochondria (1992)
    Springer
    Amino acids 2 (1992), S. 143-155 
    Details
    ISSN: 1438-2199
    Keywords: Amino acids ; Cysteine metabolism ; 3-Mercaptopyruvate pathway ; Sulfate formation ; Mitochondria ; Glutathione
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We have studied the 3-mercaptopyruvate pathway (transamination pathway) ofl-cysteine metabolism in rat liver mitochondria.l-Cysteine and other substrates at 10 mM concentration were incubated with mitochondrial fraction at pH 8.4, and sulfate and thiosulfate were determined by ion chromatography. Whenl-cysteine alone was incubated, sulfate formed was 0.7µmol per mitochondria from one g of liver per 60 min. Addition of 2-oxoglutarate and GSH resulted in more than 3-fold increase in sulfate formation, and thiosulfate was formed besides sulfate. The sum (A + 2B) of sulfate (A) and thiosulfate (B) formed was approximately 7-times that withl-cysteine alone. Incubation with 3-mercaptopyruvate resulted in sulfate and thiosulfate formation, and sulfate was formed with thiosulfate. These reactions were stimulated with glutathione. Sulfate formation froml-cysteinesulfinate and 2-oxoglutarate was not enhanced by glutathione and thiosulfate was not formed. These findings indicate thatl-cysteine was metabolized and sulfate was formed through 3-mercaptopyruvate pathway in mitochondria.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00806085
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