PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Pyroglutamate Hydrolase”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 37 records · Page 2Linked to original sources
PubMed1997

Growth failure, encephalopathy, and endocrine dysfunctions in two siblings, one with 5-oxoprolinase deficiency.

UNLABELLED: Two female siblings, born to consanguineous parents, presented with a similar phenotype characterized by severe growth and developmental failure, dysmorphic features, thyroid and gonadal dysfunction, autistic traits and hand stereotypes resembling Rett syndrome. In the elder patient, analysis of urinary organic acids disclosed a very high excretion of 5-oxoproline (4.2 to 8.1 mol/mol creatinine) and enzyme assays of leucocyte extracts revealed a profound deficiency of 5-oxoprolinase. However, normal urinary organic acid profiles were found in the younger child. In view of their distinct dysmorphic features and severe growth deficiency, these siblings cannot be considered as Rett Syndrome variants. The Dubowitz and carbohydrate-deficient glycoprotein syndromes were also excluded clinically and biochemically respectively. We conclude that these patients suffer from a hitherto undescribed autosomal recessive disorder, unrelated to the 5-oxoprolinase deficiency of the elder sib. CONCLUSION: The present findings give evidence that 5-oxoprolinase deficiency is not associated with a distinct morbid phenotype.

Brain Diseases↗
PubMed1999

5-Oxoprolinuria in patients with and without defects in the gamma-glutamyl cycle.

UNLABELLED: In patients with defects in the synthesis, breakdown and metabolism of glutathione (GSH), like glutathione synthetase deficiency (GSD) and 5-oxoprolinase deficiency, urinary excretion of 5-oxoproline, an intermediate of the gamma-glutamyl cycle, is increased. We identified 20 patients with significantly elevated urinary excretion of 5-oxoproline (> or =150 mmol/mol creatinine) during 5 years of selective screening for organic acidurias. In 6 of them, 5-oxoprolinuria was a constant finding including three patients with GSD and one with 5-oxoprolinase deficiency. One patient with constant 5-oxoprolinuria had GM2 gangliosidosis and one was clinically unaffected. In 14 patients, 5-oxoprolinuria was a transient abnormality and most often associated with an inborn error of metabolism outside the gamma-glutamyl cycle. In 9 of them 5-oxoprolinuria was associated with a neonatal urea cycle defect, with tyrosinaemia type I or occurred during metabolic decompensation in propionic acidaemia or methylmalonic acidaemia. Additionally, transient 5-oxoprolinuria was associated with homocystinuria, Stevens-Johnson syndrome, paracetamol intoxication, vigabatrin medication or extreme prematurity. CONCLUSION: 5-Oxoprolinuria is a more common condition than hitherto thought and is primarily associated with defects in the gamma-glutamyl cycle. However, several other inborn errors of metabolism and pathophysiological conditions must be taken into account when discovering 5-oxoprolinuria.

Adolescent↗
PubMed2006

Persistent 5-oxoprolinuria with normal glutathione synthase and 5-oxoprolinase activities.

5-Oxoprolinuria is primarily associated with inborn errors of the gamma-glutamyl cycle. In addition, transient 5-oxoprolinuria has been reported to occur in a variety of conditions, such as prematurity and malnutrition, and during medication. We report an unusual case of permanent 5-oxoprolinuria. The patient presented 3 days after birth with acidosis, and metabolic screening revealed massive excretion of 5-oxoproline. Following recovery, growth and psychomotor development were normal, but 5-oxoprolinuria persisted. Primary defects in the gamma-glutamyl cycle were ruled out since glutathione synthase and 5-oxoprolinase activities were normal. All known secondary causes of 5-oxoprolinuria were also excluded, leaving the basis of the permanent 5-oxoprolinuria in this patient unresolved.

Child↗
PubMed1978

Enzymes of the gamma-glutamyl cycle in 'aging' WI-38 fibroblasts and in HeLa S3 cells.

gamma-Glutamyltransferase ((5-glutamyl)-peptide:amino-acid 5-glutamyltransferase, EC 2.3.2.2) activity of WI-38 fibroblasts decreased only slightly in relation to a constant amount of cell-associated protein as the cells were carried in culture serially from middle to late passage numbers leading toward senescence, e.g., from population doubling level 27 through 41. Also, when the enzyme activity was expressed on the basis of a unit number of cells or unit amount of DNA, little change occurred over that range of PDLs. As the culture approached 'phase-out', the transferase activity rose sharply regardless of how the activity was expressed. The possibility is considered that the large increase in activity could be a reflection of a significant increase in size of cells and therefore changes in the membranes where the transferase is located. The occurrence of other enzymes of the 'gamma-glutamyl cycle' in WI-38 and HeLa S3 cells also was demonstrated. These included gamma-glutamylcyclotransferase ((gamma-L-glutamyl)-L-amino-acid gamma-glutamyltransferase (cyclizing), EC 2.3.2.4) and 5-oxoprolinase, whose activities showed no large increase comparable to that of the gamma-glutamyltransferase, as the culture approached 'phase-out'.

Cell Division↗
PubMed1998

Sensitization effect of L-2-oxothiazolidine-4-carboxylate on tumor cells to melphalan and the role of 5-oxo-L-prolinase in glutathione modulation in tumor cells.

5-Oxo-L-prolinase (5-OPase) (EC 3.5.2.9) links the synthesis and metabolism of glutathione (GSH) in the gamma-glutamyl cycle. Previous studies showed that L-2-oxothiazolidine-4-carboxylate (OTZ), a 5-oxo-L-proline analog that is metabolized by 5-OPase, can preferentially decrease the cellular GSH levels in vivo in rat mammary tumors and sensitizes the tumors to the alkylating agent melphalan. The present study investigated the biochemical mechanism of this effect in a human breast cancer cell line, MCF7. We found that OTZ decreased the GSH levels in MCF7 cells. When the cells were treated with OTZ plus melphalan, the cytotoxicity of melphalan was increased as compared with that of melphalan alone, and this effect could be reversed by the addition of glutamate, which is the product of 5-OPase reaction and a critical substrate in GSH synthesis. We concluded that OTZ increases melphalan toxicity by limiting glutamate production from 5-OPase for GSH synthesis. We also observed that the expression of 5-OPase in the stably transfected MCF7 cells decreased the cellular GSH contents, sensitized the cells to melphalan toxicity, and diminished the sensitizing effect of OTZ. Furthermore, exposure to the GSH-depleting agent buthionine sulfoximine led to increased expression of 5-OPase in both MCF7 cells and the peripheral blood mononuclear cells of patients. These results indicate a critical interaction between cellular GSH levels and 5-OPase activity that could be important in GSH modulation in therapeutic settings.

Antineoplastic Agents, Phytogenic↗
PubMed1998

Patients with genetic defects in the gamma-glutamyl cycle.

In the gamma-glutamyl cycle, hereditary defects have been described in four of the six enzymes namely: gamma-GC synthetase; GSH synthetase; gamma-glutamyl transpeptidase and 5-oxoprolinase. Mutants are still to be found in gamma-glutamyl cyclotransferase and in the dipeptidase. Deficiency of GSH synthatase or gamma-GC synthetases results in low levels of GSH. In gamma-GC synthetase deficiency hemolytic anemia is the most prominent symptom, with or without hepatosplenomegaly. In generalized GSH synthetase deficiency 5-oxoproline is overproduced due to lack of feedback inhibition of gamma-GC synthetase. These patients have metabolic acidosis, 5-oxoprolinuria, hemolytic anemia and about 50% of them also have progressive neurological symptoms. Treatment includes acidosis correction, high doses of vitamin E and C and avoidance of drugs precipitating hemolytic crises in G6PD deficiency. Therapeutic trials with GSH analogues, N-acetylcysteine and GSH esters have been carried out. Glutathione synthetase deficiency restricted to erythrocytes results in hemolytic anemia but no 5-oxoprolinuria. gamma-Glutamyl transpeptidase deficiency is associated with GSH-emia and GSH-uria whereas 5-oxoprolinase deficiency is associated with 5-oxoprolinuria. In diagnostic work it must be emphasized that erythrocytes contain an incomplete gamma-glutamyl cycle; they lack both gamma-glutamyl transpeptidase and 5-oxoprolinase and these enzyme activities must therefore be analyzed in other types of cells such as leukocytes and fibroblasts. It is also important to investigate other patients with inherited defects in the gamma-glutamyl cycle to learn more about the biological role of GSH in man.

Erythrocytes↗
PubMed1998

Potential for selective modulation of glutathione in cancer chemotherapy.

Notwithstanding ongoing progress in anticancer therapeutics development, the persistent problem remains to selectively target tumors while sparing normal tissues. This is confounding largely because the differences between normal and tumor cells are often subtle and part of a gradient, where a gene product may be more or less expressed in tumor compared with the host normal tissue, but seldom expressed (or turned off) in tumors. The role of glutathione (GSH) and related enzymes in cellular resistance to xenobiotics, including chemotherapy is well established. This study is among those attempting to modulate GSH to therapeutic advantage. The authors briefly describe the experience with the gamma-glutamylcysteine synthetase inhibitor buthionine sulfoximine, and then in greater detail outline recent evidence for a potentially more selective approach using the cysteine prodrug L-2-oxothiazolidine-4-carboxylate. This has led to a detailed study of the activating enzyme 5-oxo-L-prolinase, including enzymatic and immunocharacterization, as well as in vitro study of the effect of its modulators on anticancer drug toxicity. Using high affinity antibodies the authors have generated interesting information on the distribution of this enzyme in tumor versus normal human tissues. Finally, the authors have been studying the potential for modulating gap junctions as a part of anti-cancer therapeutics, since they transport GSH between cells and are generally deficient in tumor cells. Preliminary studies suggest that gap junction induction may dramatically deplete GSH concentration in tumor cells and sensitize them to a variety of treatments.

Animals↗
PubMed1999

Immunohistochemical localization of 5-oxo-L-prolinase, an enzyme of the gamma-glutamyl cycle, in porcine brain microvessels.

The immunohistochemical analysis of the distribution of 5-oxo-L-prolinase in porcine brain at the light microscopic level was performed with an antibody raised against the enzyme purified from pig kidney. The present study reveals the specific expression of 5-oxo-L-prolinase in brain capillaries with an average diameter of 4.1+/-0.9 microm, while larger blood vessels remain unstained. Porcine kidney and skeletal muscle show no endothelial-specific staining with the antibody. In some cases, the asymmetrical staining pattern in cross and longitudinal sections of brain microvessels indicate endothelial- but also pericyte-specific expression.

Animals↗