Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.5.1.18 (glutathione S-transferase)
 22,582 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Non-specific carboxylesterases (carboxylesterases) and glutathione S-transferases (GSTs) are two groups of drug metabolizing enzymes responsible for hydrolysis and glutathione conjugation of xenobiotics. This study was conducted to determine the following: (1) the distribution of carboxylesterase and GST activities in different rat liver cells, (2) the effects of vitamin A deficiency (A-) on the absolute activities and on the distribution of carboxylesterases and GSTs in rat liver. Rat livers were fractionated into parenchymal and non-parenchymal cells by means of collagenase perfusion and differential centrifugation. Non-parenchymal cells were further fractionated by means of Percoll density gradient centrifugation into a layer of Kupffer cells and another layer containing stellate and endothelial cells. Carboxylesterase and GST activities were determined in these fractions. show that: (1) both carboxylesterases and GSTs were mainly localized in the parenchymal fraction, (2) there was no significant difference between male and female rats with regard total activity or distribution of carboxylesterases and GSTs in rat liver cells, (3) A- caused a highly significant reduction in carboxylesterase and GST activities in total liver homogenates and parenchymal cells. This reduction was not ameliorated by administration of retinoic acid 18 hr before sacrifice of animals. These results open up a new era of investigations about the potential role of vitamin A in the regulation of detoxification enzymes.
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PMID:The distribution of non-specific carboxylesterases and glutathione S-transferases in different rat liver cells. Effects of vitamin A deficiency. 804 15

Male and female C57B1/6 mice were rendered vitamin A-deficient, and the effects of this deficiency on certain xenobiotic-metabolizing enzymes and defenses against oxidative stress were examined. Vitamin A deficiency significantly increased the levels of DT-diaphorase, glutathione transferase, and catalase in the hepatic cytosolic fraction from male mice (5.2-, 1.6-, and 3.5-fold, respectively), as well as from female mice (4.8-, 3.3-, and 2.4-fold, respectively). In the hepatic mitochondrial fraction (containing peroxisomes) from male animals, the activities of urate oxidase and catalase were increased 3.4- and 1.7-fold, respectively. The activity of catalase in the mitochondrial fraction from female mice was not affected by vitamin A deficiency, whereas the activity of peroxisomal urate oxidase was increased 2.9-fold. The hepatic level of ubiquinone was increased somewhat. The significance of the increases observed here is presently unclear, but it may be speculated that vitamin A and/or its metabolites are somehow involved in the down-regulation of these proteins. Another possibility is that these enzymes are increased as a result of hepatic oxidative stress caused by vitamin A deficiency. However, vitamin A deficiency had no effect on the activity of superoxide dismutase in this study, whereas the activity of glutathione peroxidase was slightly decreased (27%) in the hepatic cytosolic fraction from male mice. In addition, the hepatic level of alpha-tocopherol was decreased dramatically in the vitamin A-deficient animals.
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PMID:Effects of vitamin A deficiency on selected xenobiotic-metabolizing enzymes and defenses against oxidative stress in mouse liver. 1064 45


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