Glutathione-dependent reductive

The most active diaryl telluride, bis(4-aminophenyl)telluride, demonstrated 348%, 530%, 995% and 900% of the catalytic activity of ebselen for the glutathione-dependent reduction of H2O2, f-butylhydroperoxide (TBH), cumene hydroperoxide and linoleic acid peroxide, respectively. ... 

Nemeti, B. and Gregus, Z. (2007) Glutathione-dependent reduction of arsenate by glycogen phosphorylase — A reaction coupled to glycogenolysis. Toxicological Sciences, 100(1), 36-43. 

III. Glutathione reductase (EC 1.6.4.2) It is a flavoprotein that catalyzes the NADPH-dependent reduction of oxidized glutathione (GSSG) to glutathione (GSH). This enzyme is essential for the GSH redox cycle which maintains adequate levels of reduced cellular GSH. A high GSH/GSSG ratio is essential for protection against oxidative stress. 

Figure 3.5 gives a schematic overview of the major pathways that are involved in the degradation of substrate 2. To cut a long story short, it is the cytosolic glutathione-dependent pathways II-VI which predominantly compete with reductive pathway I [35, 62]. 

Glutathione reductase, thioredoxin reductase, and lipoamide dehydrogenase are members of a group of flavoproteins that contain an active site disulfide as well as FAD. They catalyze the NAD(P)H dependent reduction of a disulfide... 

As shown in Figure 13.3, oxidation of ascorbic acid, for example, by the reduction of superoxide to hydrogen peroxide or Fe + to Fe +, and similar reduction of other transition metal ions, proceeds by a one-electron process, forming the monodehydroascorbate radical. The radical rapidly disproportionates into ascorbate and dehydroascorbate. Most tissues also have both nicotinamide adenine dinucleotide phosphate (NADPH) and glutathione-dependent monodehydroascorbate reductases, which reduce the radical back to ascorbate. Ascorbate is thus an effective quencher of singlet oxygen and other radicals. 

As a component of glutathione peroxidase and the iodothyronine 5 -deiodinases, selenium is an essential micronutrient for humans. Its role in the deiodinase enzymes may be one reason that children require more selenium for growth than adults. Selenium is also a component of the enzyme thioredoxin reductase, which catalyses the NADPH-dependent reduction of the redox protein thioredoxin. Other selenium-containing proteins of unknown functions, including selenoprotein P found in the plasma, have also been identified. Excess selenium administered as selenite and selenate has been shown to be metabolized to methylated compounds and excreted. 

As for organic nitrate esters such as nitroglycerine and isosorbide dinitrate, the mechanism of their vasodilating action is now believed to result from their reduction to nitric oxide (NO). Thiols, and particularly glutathione, play an important role in this activation. In the first step, a thionitrate is formed (reaction 10-A) whose N-reduction may occur by more than one route. For example, a GSH-dependent reduction may yield nitrite (reaction 10-B), which undergoes further reduction to NO S-nitrosoglutathione (GS—NO) has also been postulated as an intermediate. 

C. fasciculata (52-54) and T. cruzi (55-57). The enzyme, which has been found located only in the cytosol of T. brucei (58), catalyzes the NADPH-dependent reduction of trypanothione, but not glutathione. Ultimately, dihydrotrypanothione is capable of undergoing a rapid non-enzymatic disulfide exchange reaction with intracellular disulfides (RSSR), among them oxidized glutathione and cysteine (59). This reaction is summarized as ... 

Glutathione (GSH) peroxidase (EC 1.11.1.9) is one of several selenoproteins that contain a unique selenocysteine residue at the active site (1). This enzyme catalyzes the GSH-dependent reduction of both hydrogen peroxide and organic hydroperoxides, including fatty acid hydroperoxides formed during lipid peroxidation. GSH peroxidase activity has been measured in both protozoan and helminth parasites (11,12). The enzyme from Schistosoma mansoni has been cloned (13). The presence of the unique selenocysteine codon (UGA) confirms that it is a selenoprotein. Although GSH peroxidase activity appears to be absent from Hymenolepsis dimimta and M. expansa... 

In human G6PD-deficient red blood cells, an aqueous extract of bupleurum demonstrated dose-dependent reduction of reduced glutathione (GSH) and methemoglobin (MetHb) at concentrations of 5-10 mg/ml (Ko et al. 2008). 

Experiments have been reported elsewhere in which chlorophyll, as well as other alcohol-soluble material, was removed from chloroplast fragments, and a light-dependent reduction of oxidized glutathione, via the TPN-linked yeast glutathione reductase, was observed upon recombination of the chlorophyll extract with the colorless fraction (374a). 

---