Mitochondrial glutathione in liver does not arise by intramitochondrial synthesis, but rather from the cytoplasm, by a process characterized by slow net transport and more rapid exchange transport.

Animals↗

PubMed1985

[Total abdominal irradiation following combination chemotherapy and second-look laparotomy in the treatment of advanced ovarian cancer].

From 1980 to 1984 fifty-four patients with advanced ovarian carcinoma after operation and concluding chemotherapy with alkeran (n = 7) or cis-platin/alkeran +/- hexamethylmelamine (n = 47) as well as second-look laparotomy received follow-up radiotherapy either with the moving-strip technique (n = 35) or later the open-field technique (n = 19). 32 patients in CR received radiation therapy. 15 patients in CR are without relapse after undergoing open-field radiation therapy and a mean observation period of 25 months. At this point of time 5 of 17 patients had relapses under the moving-strip radiation treatment. The frequency of the relapses is apparently due to the very long periods of radiation and numerous interruptions in treatment. If residual tumors were present at the begin of ray therapy, a CR could only be achieved in cases where the previous monotherapy was with alkeran.

Adenocarcinoma↗

PubMed1984

Extracellular metabolism of glutathione accounts for its disappearance from the basolateral circulation of the kidney.

Glutathione labeled in each of its amino acid residues, the corresponding free amino acids, and gamma-glutamyl-amino acids were used to evaluate their renal basolateral transport and metabolism at physiological levels of glutathione. Recovery of label in the venous outflow was compared to that of co-administered inulin after a single-pass in vivo infusion of rat kidney. Metabolites of glutathione and of its constituent amino acids were determined. No net basolateral transport of glutathione was detected; instead there was extensive breakdown of glutathione by the actions of basolateral gamma-glutamyl transpeptidase and dipeptidase. Glutamate and 5-oxoproline showed net basolateral uptake. Recoveries of 35S greater than those of inulin were found after perfusion of [35S]cysteine and [35S]glutathione suggesting rapid net tubular reabsorption of cyst(e)ine. Recovery of label from perfused [U-14C]glycine was equivalent to that of inulin consistent with little or no net flux. Co-administration of large amounts of unlabeled metabolites together with the labeled glutathiones led to label recoveries closer to those of inulin, consistent with competitive inhibition of labeled metabolite transport. Treatment of rats with an inhibitor of gamma-glutamyl transpeptidase decreased basolateral glutathione metabolism and thus indirectly decreased transport of labeled metabolites. No net basolateral transport of gamma-glutamyl-amino acids was detected. Significant amounts of label perfused as [Glu-U-14C]glutathione appeared in the gamma-glutamyl-amino acid fraction of the renal venous outflows, providing direct evidence that glutathione is used in vivo for the formation of gamma-glutamyl-amino acids.

Animals↗

PubMed1984

Reversible dissociation of gamma-glutamylcysteine synthetase into two subunits.

gamma-Glutamylcysteine synthetase (rat kidney; Mr approximately 104,000) is composed of 2 nonidentical subunits. In the present work, a procedure was developed for the reversible dissociation of the enzyme into its subunits (Mr = 73,000 and 27,700) under nondenaturing conditions. Students in which gel electrophoresis was used, in conjunction with an enzyme activity stain and elution and re-electrophoresis of protein bands, showed that the heavy subunit contains all of the structural requirements for enzymatic activity and also for feedback inhibition of the enzyme activity by glutathione. The light subunit, which may be formed from a precursor protein, has a significantly lower content of Trp, Phe, Tyr, Val, and Ala residues than the heavy subunit, while its content of Lys, His, Met, and Asx residues is higher.

Adenosine Triphosphate↗

PubMed1984

Resolution of 5-oxo-L-prolinase into a 5-oxo-L-proline-dependent ATPase and a coupling protein.

5-Oxo-L-prolinase catalyzes a reaction in which the endergonic cleavage of 5-oxo-L-proline to form L-glutamate is coupled to the exergonic cleavage of ATP to ADP and Pi. In the present research, the enzyme present in a strain of Pseudomonas putida isolated from soil by enrichment culture was found to be composed of two protein components. Neither component alone could catalyze the 5-oxoprolinase reaction, but the reaction was effectively catalyzed when they were mixed. One component (A) exhibited 5-oxo-L-proline-dependent ATPase activity indicating that Component A can interact with both ATP and 5-oxo-L-proline. The other component (coupling protein; B) does not exhibit ATPase activity nor is there evidence that it binds 5-oxo-L-proline. The findings are consistent with (but do not prove) the hypothesis that the Component A catalyzes an initial step in the reaction which involves 5-oxoproline and ATP, such as phosphorylation of 5-oxoproline. The coupling protein (B) may function as a catalyst that converts a phosphorylated form of 5-oxoproline to glutamate, or it might alter the conformation of Component A so as to facilitate the reaction.

Adenosine Triphosphatases↗

PubMed1984

Synthesis of L-2-oxothiazolidine-4-carboxylic acid.

An improved synthesis of L-2- oxothiazolidine -4-carboxylic acid is described. The new procedure, which leads to excellent yields of product, does not require the use of phosgene. The new method is thus less hazardous than the original one, and is readily adaptable to the preparation of 35S-labeled product.

Chlorobenzoates↗

PubMed1984

Gamma-glutamylcysteine synthetase. Interactions of an essential sulfhydryl group.

gamma-Glutamylcysteine synthetase (isolated from rat kidney) has one sulfhydryl group that reacts with 5,5'-dithiobis-(2-nitrobenzoate). This single exposed sulfhydryl group is not required for enzyme activity. The enzyme is potently inactivated by cystamine, which apparently interacts with a sulfhydryl group at the active site to form a mixed disulfide. 5,5'-Dithiobis-(2-nitrobenzoate) does not interact with the sulfhydryl group that reacts with cystamine. After the enzyme was 90% inactivated by reaction with cystamine, 3.4 mol of 5,5'-dithiobis-(2-nitrobenzoate) reacted per mol of enzyme, indicating that binding of cystamine exposes sulfhydryl groups which are apparently buried or unreactive in the native enzyme. L-Glutamate (but not D-glutamate or L-alpha-aminobutyrate) protected against inactivation by cystamine. In contrast, ATP enhanced the rate of inactivation by cystamine, and the apparent Km value for this effect is similar to that for ATP in the catalytic reaction. Studies on the structural features of cystamine that facilitate its interaction with the enzyme showed that selenocystamine, monodansylcystamine, and N-[2[2-aminoethyl)-dithio)ethyl]-4-azido-2-nitrobenzeneamine are also good inhibitors. Whereas S-(S-methyl)cysteamine-Sepharose does not interact with the enzyme (Seelig, G. F., and Meister, A. (1982) J. Biol. Chem. 257, 5092-5096), S-(S-methyl)cysteamine is a potent inhibitor; 1 mol of this compound completely inactivated 1 mol of enzyme. In the course of this work, a useful modification of the method for isolating this enzyme from kidney was developed.

Animals↗

PubMed1984

Gamma-glutamylcysteine synthetase from erythrocytes.

gamma-Glutamylcysteine synthetase was isolated by means of a three-step method in highly active (specific activity, about 1400 units/mg) and apparently homogeneous form from rat erythrocytes. The enzyme has a molecular weight of about 100,000, and is composed of two subunits (Mr approximately 75,000 and 25,000). The erythrocyte enzyme exhibits physicochemical, catalytic, and immunological properties that closely resemble those displayed by rat kidney gamma-glutamylcysteine synthetase. The isolation procedure described here, which was also successfully applied to isolation of the enzyme from sheep erythrocytes, may be useful in exploring the properties of mutant forms of the enzyme.

Animals↗