Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.5.1.47 (cysteine synthase)
 625 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Elevation of glutathione (GSH) is commonly observed in cellular resistance to a number of anticancer agents. Most frequently reported change in GSH metabolism that is associated with the elevated GSH levels is increased mRNA expression and activity of gamma-glutamyl cysteine synthetase (gamma GCS), the first enzyme of the GSH biosynthetic pathway. We have isolated sublines of the A2780 ovarian carcinoma cell line (C10 and C25) that are 8- and 12-fold resistant to oxaliplatin by repeatedly exposing the cells to increasing concentrations of the platinum agent. The GSH levels in C10 and C25 cell sublines are 3.1- and 3.8-fold higher than the parent A2780 cell line. The mRNA levels and activities for gamma GCS and that for gamma-glutamyl transpeptidase (gamma GT), the GSH salvage pathway enzyme, were measured in these cells. The mRNA for gamma GT and gamma GCS were measured by RT-PCR, with quantitation of the PCR product by HPLC; mRNA levels are expressed as ratios to beta-actin mRNA, used as an endogenous standard. GSH and gamma GCS activity were measured by HPLC assays and gamma GT activity by a colorimetric assay. The increase in GSH in C10 and C25 was associated with an elevation in gamma GT mRNA (2.5- and 8-fold) and gamma GT activity (2.7- and 2.8-fold). No changes were observed in gamma GCS mRNA levels or activity. The data indicate that alterations in GSH metabolism leading to elevations in cellular GSH in A2780 ovarian carcinoma cells selected for low levels of resistance to oxaliplatin are mediated by gamma GT, the "salvage' pathway, rather than an increase in GSH biosynthesis.
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PMID:Altered glutathione metabolism in oxaliplatin resistant ovarian carcinoma cells. 868 32

A wide range of pollutants in the aquatic environment have the capacity to induce toxic effects expressed as cellular oxidative stress. In the current study, the potential of an in vitro toxicity testing system was therefore investigated using rainbow trout (Oncorhynchus mykiss) hepatocytes to assess different endpoints of oxidative stress. The pro-oxidants CuSO(4) and paraquat were used as models for comparison to a complex environmental sample. Results following 6, 24, 48 and 96h exposure to different concentrations of these substances show cellular effects on intracellular ROS formation, glutathione levels and redox status, expression of the antioxidant enzymes superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, gamma-glutamyl-cysteine synthetase (GCS) and thioredoxin, as well as cytotoxicity parameters. The most consistent effects (maximum values within brackets), observed in dose and time parameters for both model compounds and environmental sample, were the depletion of total glutathione (9.4% of control), induced levels of oxidized glutathione (695% of control), and gene expression regulation depicted relative to the control gene beta-actin of GCS mRNA (239% of control) and catalase (29% of control). In conclusion, the responses on several antioxidant defence system parameters demonstrated the validity of the in vitro toxicity testing system. Not only could multiple effects be detected at sub-lethal exposure concentrations, but these effects also gave valuable insight to the toxic mechanisms at the molecular level.
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PMID:Oxidative stress responses in rainbow trout (Oncorhynchus mykiss) hepatocytes exposed to pro-oxidants and a complex environmental sample. 2011 53