The effects of the sulfhydryl reducing agents 2-mercaptoethanol and dithiothreitol on wortmannin-induced inhibition of phosphoinositide 3-kinase (PI3K) were studied in order to examine whether the sulfhydryl reducing agents directly affect the wortmannin inhibition of PI3K. These reducing agents are commonly used to stabilize enzyme structures by maintaining protein sulfhydryl groups in the red...

Tyrosine hydroxylase (TH) is the initial and rate-limiting enzyme in the biosynthesis of dopamine (DA). TH activity is significantly diminished in Parkinson's disease (PD) and by the neurotoxic amphetamines, thereby accentuating the reductions in DA associated with these conditions. Reactive oxygen and nitrogen species have been implicated in the damage to DA neurons seen in PD and in reaction ...

Evidence is presented that four sulfhydryl residues play a critical role in the activity of pyruvate kinase. Modification of the four most reactive sulfhydryl groups by 5,5’-dithiobis(Z-nitrobenzoate) leads to a disulfide interchange reaction in which a chemically modified but catalytically active enzyme is produced. This form, which contains 5-thio-Z-nitrobenzoate in disulfide linkage to cyste...

Saccharopine dehydrogenase (e-N-(L-glutaryl-2)-L1ysine:NAD oxidoreductase (L-lysine-forming) EC 1.5.1.7) is inhibited by a variety of sulfhydryl reagents. Althoughp-chloromercuribenzoate and 5,5’-dithiobis(2nitrobenzoate) react with three sulfhydryl groups present in the enzyme, reaction with one reactive sulfhydryl group leads to complete loss of catalytic activity. Amino acid analysis of the ...

The number of reactive cysteine residues of yeast RNA polymerase I was determined and their function was studied using parachloromercury benzoate (pCMB), dithiobisnitrobenzoate (DTNB) and N-ethyl-maleimide (NEM) as modifying agents. By treatment with DTNB about 45 sulfhydryl groups react in the presence of 8M urea. Under non-denaturing conditions only 20 sulfhydryl groups are reactive with pCMB...

Incubation of the complex metalloflavoprotein, assimilatory nitrate reductase with N-ethylmaleimide, or a spin-labeled analog, 4-maleimido-2,2,6,6-tetramethylpiperidinooxyl, resulted in a time-dependent inactivation of NADH:nitrate reductase and NADH: cytochrome-c reductase activity with no effect on reduced methyl viologen:nitrate reductase activity. Inactivation of the enzyme, which could be ...

several studies have shown that hepatocyte membrane composition changes in patients with cholestasis and cirrhosis. these alterations that are because of intracellular oxidative stress are supposed to be reflected in erythrocyte membrane. the aim of this study was to investigate the modification of erythrocyte membrane along with hexokinase and antioxidant enzymes during development of cirrhosi...

Controlled conditions have been found that give complete reactivation and long term stabilization of rhodanese (EC 2.8.1.1) after oxidative inactivation by hydrogen peroxide. Inactivated rhodanese was completely reactivated by reductants such as thioglycolic acid (TGA) (100 mM) and dithiothreitol (DTT) (100 mM) or the substrate thiosulfate (100 mM) if these reagents were added soon after inacti...

Studies of isolated intact spinach (Spinacia oleracea L.) chloroplasts reveal that most of the available sulfhydryl groups are associated with stromal protein as opposed to a thylakoid membrane fraction under non-denaturing conditions. Increases in sulfhydryl content of approximately 50% occurred with illumination and could be correlated kinetically with a reductive activation of fructose-1,6-b...