Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effect of regucalcin, a regulatory protein in the intracellular signaling system, on superoxide dismutase (SOD) activity in the heart cytosol of normal rats and regucalcin transgenic (TG) rats was investigated. The addition of regucalcin (10(-10) to 10(-8) M) with a physiologic concentration in the enzyme reaction mixture containing the heart cytosol obtained from normal rats caused a significant increase in SOD activity, indicating that regucalcin directly activates the enzyme. The effect of regucalcin (10(-8) M) in increasing SOD activity was not seen in the presence of dithiothreitol (DTT; 0.1 or 1.0 mM), a protecting reagent for sulfhydryl group, or N-ethylmaleimide (NEM; 0.1 or 1.0 mM), a modifying reagent for sulfhydryl group, in the reaction mixture, indicating that regucalcin does not affect the sulfhydryl group. The addition of zinc sulfate (10(-6) to 10(-4) M) in the reaction mixture did not cause a significant change in SOD activity, while the enzyme activity was markedly decreased in the presence of cupric sulfate (10(-6) to 10(-4) M). The activatory effect of regucalcin (10(-8) M) on SOD was seen in the presence of zinc (10(-4) M), while not observed in the presence of copper (10(-4) M). Moreover, SOD activity was significantly enhanced in the heart cytosol of regucalcin TG rats as compared with that of normal rats. This study demonstrates that regucalcin increases SOD activity in the heart cytosol of rats, and that its effect is not related to the sulfhydryl group of enzymes.
Int J Mol Med 2004 Oct
PMID:Regucalcin increases superoxide dismutase activity in the heart cytosol of normal and regucalcin transgenic rats. 1537 3

The apicomplexan parasite Toxoplasma gondii is highly susceptible to oxidative stress caused by tert-butyl-hydroperoxide, juglone, and phenazine methylsulfate with IC(50) in the nanomolar range. Using dichlorofluorescein diacetate, a detector of endogenous oxidative stress, it was shown that juglone and phenazine methylsulfate are potentially toxic to the parasites without affecting the host cells. These results demonstrate that T. gondii is vulnerable to oxidative challenge that results from disruption of its redox balance and so this could be an effective approach to therapeutic intervention. This study has characterized redox active and antioxidant peroxidases belonging to the class of 1-Cys and 2-Cys peroxiredoxins that play crucial roles in maintaining redox balance. The tachyzoite stages of T. gondii express thioredoxin (TgTrx), 1-Cys peroxiredoxin (TgTrx-Px2), and a 2-Cys peroxiredoxin (TgTrx-Px1) and immunofluorescent studies revealed that all three proteins are located in the cytosol of the parasite confirming previous studies on TgTrx-Px1 (Kwok, L.Y., Schluter, D., Clayton, C., and Soldati, D. (2004) Mol. Microbiol. 51, 47-61). TgTrx-Px1 showed K(m) values for H(2)O(2) and tert-butyl hydroperoxide in the nanomolar range, emphasizing the great affinity of the protein for theses substrates. Moreover, the catalytic efficiency of TgTrx-Px1 for these substrates at 10(6)-10(7) M(-1) s(-1) is unusually high, which qualifies the enzyme as an extremely potent antioxidant. Kinetic analyses revealed that TgTrx-Px1 is inhibited by tert-butyl hydroperoxide, and apparent inhibition constants were determined to be between 33 and 35.6 microm depending on the concentration of the non-inhibitory substrate thioredoxin. TgTrx-Px2 protected glutamine synthetase from inactivation by Fe(3+)/DTT, showing that it is an active peroxiredoxin.
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PMID:Peroxiredoxin-linked detoxification of hydroperoxides in Toxoplasma gondii. 1550 57

The activity of many RNases requires the formation of one or more disulfide bonds which can contribute to their stability. In this study, we show that RNase activity and, to a much lesser extent, nuclease activity, are redox regulated. Intracellular RNase activity was altered in vitro by changes in the glutathione redox state. Moreover, RNase activity was abolished following exposure to reducing agents such as beta-ME or DTT. Following reduction with glutathione (GSH), RNase activity could be fully reactivated with oxidized glutathione (GSSG). In contrast, RNase activity could not be reactivated when reduced with DTT. Decreasing the level of glutathione in vivo in wheat increased RNase activity. Tobacco engineered to have an increased glutathione redox state exhibited substantially lower RNase activity during dark-induced senescence. These results suggest that RNase activity requires the presence of one or more disulfide bonds that are regulated by glutathione and demonstrate for the first time that RNase activity can be altered with an alteration in cellular redox state.
Plant Mol Biol 2004 May
PMID:RNase activity requires formation of disulfide bonds and is regulated by the redox state. 1560 66

In general, oxidative stress, the consequence of an aerobic lifestyle, induces bacterial antioxidant defence enzymes. Here we report on a peroxiredoxin of Rhizobium etli, prxS, strongly expressed under microaerobic conditions and during the symbiotic interaction with Phaseolus vulgaris. The microaerobic induction of the prxS-rpoN2 operon is mediated by the alternative sigma factor RpoN and the enhancer-binding protein NifA. The RpoN-dependent promoter is also active under low-nitrogen conditions through the enhancer-binding protein NtrC. An additional symbiosis-specific weak promoter is located between prxS and rpoN2. Constitutive expression of prxS confers enhanced survival and growth to R. etli in the presence of H2O2. Single prxS mutants are not affected in their symbiotic abilities or defence response against oxidative stress under free-living conditions. In contrast, a prxS katG double mutant has a significantly reduced (>40%) nitrogen fixation capacity, suggesting a functional redundancy between PrxS and KatG, a bifunctional catalase-peroxidase. In vitro assays demonstrate the reduction of PrxS protein by DTT and thioredoxin. PrxS displays substrate specificity towards H2O2 (Km = 62 microM) over alkyl hydroperoxides (Km > 1 mM). Peroxidase activity is abolished in both the peroxidatic (C56) and resolving (C156) cysteine PrxS mutants, while the conserved C81 residue is required for proper folding of the protein. Resolving of the R. etli PrxS peroxidatic cysteine is probably an intramolecular process and intra- and intersubunit associations were observed. Taken together, our data support, for the first time, a role for an atypical 2-Cys peroxiredoxin against oxidative stress in R. etli bacteroids.
Mol Microbiol 2005 Feb
PMID:Defence of Rhizobium etli bacteroids against oxidative stress involves a complexly regulated atypical 2-Cys peroxiredoxin. 1568 65

The role of homocysteine for store-operated calcium influx was investigated in human umbilical cord endothelial cell line. Homocysteine significantly decreased thapsigargin-evoked Ca2+ entry, membrane hyperpolarization and actin polymerization. GSH and DTT prevented homocysteine-induced inhibition of thapsigargin-evoked Ca2+ entry, membrane hyperpolarization and actin polymerization; while GSSG had the opposite effect. Homocysteine blocked large conductance Ca2+-activated K+ (BK(Ca)) channels in a concentration-dependent manner and related to the redox status of the endothelial cells. BK(Ca) channels opener NS1619 reversed thapsigargin-evoked Ca2+ entry, membrane hyperpolarization and actin polymerization; BK(Ca) channels inhibitor iberiotoxin had the opposite effect. The findings suggest that homocysteine is involved in store-regulated Ca2+ entry through membrane potential-dependent and actin cytoskeleton-dependent mechanisms, redox status of homocysteine and BK(Ca) channels may play a regulatory role in it.
Mol Cell Biochem 2005 Jan
PMID:Homocysteine inhibits store-mediated calcium entry in human endothelial cells: evidence for involvement of membrane potential and actin cytoskeleton. 1578 15

Effects of common electrophoretic reagents, reducing agents (beta-mercaptoethanol [BME] and DTT), denaturants (SDS and urea), and non-ionic detergent (Triton X-100), on the activity and stability of bovine plasmin (b-pln) and human plasmin (h-pln) were compared. In the presence of 0.1% SDS (w/v), all reagents completely inhibited two plns, whereas SDS (1%) and urea (1 M) denatured plns recovered their activities after removal of SDS by treatment of 2.5% Triton X-100 (v/v). However, reducing agents (0.1 M of BME and DTT) treated plns did not restore their activities. Based on a fibrin zymogram gel, five (from b-pln) and four (from h-pln) active fragments were resolved. Two plns exhibited unusual stability in concentrated SDS and Triton X-100 (final 10%) and urea (final 6 M) solutions. Two bands, heavy chain-2 (HC-2) and cleaved heavy chain-2 (CHC-2), of b-pln were completely inhibited in 0.5% SDS or 3 M urea, whereas no significant difference was found in h-pln. Interestingly, 50 kDa (cleaved heavy chain-1, CHC-1) of b-pln and two fragments, 26 kDa (light chain, LC) and 29 kDa (microplasmin, MP), of h-pln were increased by SDS in a concentration dependent manner. We also found that the inhibition of SDS against both plns was reversible.
J Biochem Mol Biol 2005 Mar 31
PMID:Comparative study of enzyme activity and stability of bovine and human plasmins in electrophoretic reagents, beta-mercaptoethanol, DTT, SDS, Triton X-100, and urea. 1582 94

Histone acetylation plays an important role in regulating the chromatin structure and is tightly regulated by two classes of enzyme, histone acetyltransferases (HAT) and histone deacetylases (HDAC). Deregulated HAT and HDAC activity plays a role in the development of a range of cancers. Consequently, inhibitors of these enzymes have potential as anticancer agents. Several HDAC inhibitors have been described; however, few inhibitors of HATs have been disclosed. Following a FlashPlate high-throughput screen, we identified a series of isothiazolone-based HAT inhibitors. Thirty-five N-substituted analogues inhibited both p300/cyclic AMP-responsive element binding protein-binding protein-associated factor (PCAF) and p300 (1 to >50 micromol/L, respectively) and the growth of a panel of human tumor cell lines (50% growth inhibition, 0.8 to >50 micromol/L). CCT077791 and CCT077792 decreased cellular acetylation in a time-dependent manner (2-48 hours of exposure) and a concentration-dependent manner (one to five times, 72 hours, 50% growth inhibition) in HCT116 and HT29 human colon tumor cell lines. CCT077791 reduced total acetylation of histones H3 and H4, levels of specific acetylated lysine marks, and acetylation of alpha-tubulin. Four and 24 hours of exposure to the compounds produced the same extent of growth inhibition as 72 hours of continuous exposure, suggesting that growth arrest was an early event. Chemical reactivity of these compounds, as measured by covalent protein binding and loss of HAT inhibition in the presence of DTT, indicated that reaction with thiol groups might be important in their mechanism of action. As one of the first series of small-molecule inhibitors of HAT activity, further analogue synthesis is being pursued to examine the potential scope for reducing chemical reactivity while maintaining HAT inhibition.
Mol Cancer Ther 2005 Oct
PMID:Isothiazolones as inhibitors of PCAF and p300 histone acetyltransferase activity. 1622 1

The mechanisms through which thiol oxidation and cellular redox influence the regulation of soluble guanylate cyclase (sGC) are poorly understood. This study investigated whether promoting thiol oxidation via inhibition of NADPH generation by the pentose phosphate pathway (PPP) with 1 mM 6-aminonicotinamide (6-AN) or the thiol oxidant diamide (1 mM) alters sGC activity and cGMP-associated relaxation to nitric oxide (NO) donors [S-nitroso-N-acetylpenicillamine (SNAP) and spermine-NONOate]. Diamide and 6-AN inhibited NO-elicited relaxation of endothelium-denuded bovine pulmonary arteries (BPA) and stimulation of sGC activity in BPA homogenates. Treatment of BPA with the thiol reductant DTT (1 mM) reversed inhibition of NO-mediated relaxation and sGC stimulation by 6-AN. The increase in cGMP protein kinase-associated phosphorylation of vasodilator-stimulated phosphoprotein on Ser239 elicited by 10 microM SNAP was also inhibited by diamide. Activation of sGC by SNAP was attenuated by low micromolar concentrations of GSSG in concentrated, but not dilute, homogenates of BPA, suggesting that an enzymatic process contributes to the actions of GSSG. Relaxation to agents that function through cAMP (forskolin and isoproterenol) was not altered by inhibition of the pentose phosphate pathway or diamide. Thus a thiol oxidation mechanism controlled by the regulation of thiol redox by NADPH generated via the pentose phosphate pathway appears to inhibit sGC activation and cGMP-mediated relaxation by NO in a manner consistent with its function as an important physiological redox-mediated regulator of vascular function.
Am J Physiol Lung Cell Mol Physiol 2006 Mar
PMID:Thiol oxidation inhibits nitric oxide-mediated pulmonary artery relaxation and guanylate cyclase stimulation. 1627 75

A new simplified procedure for identifying human plasmin was developed using a DTT copolymerized agarose stacking gel (ASG) system. Agarose (1 %) was used for the stacking gel because DTT inhibits the polymerization of acrylamide. Human plasmin showed the lowest activity at pH 9.0. There was a similar catalytically active pattern observed under acidic conditions (pH 3.0) to that observed under alkaline conditions (pH 10.0 or 11.0). Using the ASG system, the primary structure of the heavy chain could be established at pH 3.0. This protein was found to consist of three fragments, 45 kDa, 23 kDa, and 13 kDa. These results showed that the heavy chain has a similar structure to the autolysed plasmin (Wu et al., 1987b) but there is a different start amino acid sequence of the N-termini.
J Biochem Mol Biol 2005 Nov 30
PMID:A method for direct application of human plasmin on a dithiothreitol-containing agarose stacking gel system. 1633 93

Ribonucleotide reductase plays a central role in cell proliferation by supplying deoxyribonucleotide precursors for DNA synthesis and repair. The holoenzyme is a protein tetramer that features two large (hRRM1) and two small (hRRM2 or p53R2) subunits. The small subunit contains a di-iron cluster/tyrosyl radical cofactor that is essential for enzyme activity. Triapine (3-aminopyridine-2-carboxaldehyde thiosemicarbazone, 3-AP) is a new, potent ribonucleotide reductase inhibitor currently in phase II clinical trials for cancer chemotherapy. Ferric chloride readily reacts with Triapine to form an Fe(III)-(3-AP) complex, which is reduced to Fe(II)-(3-AP) by DTT. Spin-trapping experiments with 5,5-dimethyl-1-pyrroline-N-oxide prove that Fe(II)-(3-AP) reduces O2 to give oxygen reactive species (ROS). In vitro activity assays show that Fe(II)-(3-AP) is a much more potent inhibitor of hRRM2/hRRM1 and p53R2/hRRM1 than Triapine. Electron paramagnetic resonance measurements on frozen solutions of hRRM2 and p53R2 show that their tyrosyl radicals are completely quenched by incubation with Fe(II)-(3-AP). However, the enzyme activity is maintained in protein samples supplemented with catalase alone or in combination with superoxide dismutase. Furthermore, catalase alone or in combination with superoxide dismutase markedly decreases the antiproliferative effect of Triapine in cytotoxicity assays. These results indicate that Triapine-induced inhibition of ribonucleotide reductase is caused by ROS. We suggest that ROS may ultimately be responsible for the pharmacologic effects of Triapine in vivo.
Mol Cancer Ther 2006 Mar
PMID:A Ferrous-Triapine complex mediates formation of reactive oxygen species that inactivate human ribonucleotide reductase. 1654 72


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