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)

The relationship between l-cystine transport and intracellular glutathione (GSH) levels was investigated in cultured pancreatic AR42J acinar and betaTC3 islet cells exposed to diethylmaleate, an electrophilic agent known to activate cellular antioxidant responses. Cystine transport was mediated predominantly by the Na+-independent anionic amino acid transport system x-c, with influx inhibited potently by glutamate and homocysteate but unaffected by cationic or neutral amino acids. Saturable cystine transport was 10-fold higher in AR42J (531 pmol (mg protein)-1 min-1) than in betaTC3 (49 pmol (mg protein)-1 min-1) cells, and GSH levels were higher in AR42J cells. Treatment with 2-mercaptoethanol increased GSH levels in betaTC3 cells from 7.5 to 36 nmol (mg protein)-1, whilst the GSH content in AR42J cells (64 nmol (mg protein)-1) was not altered significantly. Incubation of AR42J or betaTC3 cells with homocysteate (2.5 mM, 0-48 h), a competitive inhibitor of cystine transport via system x-c, reduced intracellular GSH levels and resulted in a time-dependent (6-24 h) induction of system x-c transport activity. Treatment of AR42J cells with diethylmaleate (100 microM, 0-48 h) resulted in a time- (5-10 h) and protein synthesis-dependent induction of cystine transport, with intracellular GSH levels initially decreasing and then increasing 2-fold above control levels after 24 h. Diethylmaleate also depressed GSH levels in betaTC3 cells, but cystine transport was not elevated significantly. In both AR42J and betaTC3 cells, inhibition of gamma-glutamyl cysteine synthetase by buthionine sulphoximine (100 microM, 24 h) reduced GSH levels but had no effect on cystine transport. The present findings establish that induction of system x-c leads to changes in GSH levels in pancreatic AR42J acinar and betaTC3 islet cells, with changes in the intracellular redox state stimulating transporter expression. Induction of activity of system x-c, together with adaptive increases in GSH synthesis in response to oxidative stress, may contribute to cellular antioxidant defences in pancreatic disease.
 ...
PMID:Induction of cystine transport via system x-c and maintenance of intracellular glutathione levels in pancreatic acinar and islet cell lines. 980 3

Hydrogen sulfide (H2S) is a key metabolite in biosynthesis and is increasingly being recognized as an essential gasotransmitter. Owing to its diffusible and reactive nature, H2S can be difficult to quantify, particularly in situ. Although several detection schemes are available, they have drawbacks. In efforts to quantify sulfide release in the cross-linking reaction of the flagellar protein FlgE, we developed an enzyme-coupled sulfide detection assay using the Escherichia coli O-acetylserine sulfhydrylase enzyme CysM. Conversion of HS- to l-cysteine via CysM followed by derivatization with the thiol-specific fluorescent dye 7-diethylamino-3-(4-maleimidophenyl)-4-methylcoumarin enables for facile detection and quantification of H2S by fluorescent HPLC. The assay was validated by comparison to the well-established methylene blue sulfide detection assay and the robustness demonstrated by interference assays in the presence of common thiols such as glutathione, 2-mercaptoethanol, dithiothreitol, and l-methionine, as well as a range of anions. We then applied the assay to the aforementioned lysinoalanine cross-linking by the Treponema denticola flagellar hook protein FlgE. Overall, unlike previously reported H2S detection methods, the assay provides a biologically compatible platform to accurately and specifically measure hydrogen sulfide in situ, even when it is produced on long time scales.
 ...
PMID:Design, Validation, and Application of an Enzyme-Coupled Hydrogen Sulfide Detection Assay. 3054 66