Search results for "hydrogenase"
showing 10 items of 575 documents
Quantifying the limits of transition state theory in enzymatic catalysis
2017
Significance Transition state theory (TST) is the most popular theory to calculate the rates of enzymatic reactions. However, in some cases TST could fail due to the violation of the nonrecrossing hypothesis at the transition state. In the present work we show that even for one of the most controversial enzymatic reactions—the hydride transfer catalyzed by dihydrofolate reductase—the error associated to TST represents only a minor correction to the reaction rate. Moreover, this error is actually larger for the reaction in solution than in the enzymatic active site. Based on this finding and on previous studies we propose an “enzymatic shielding” hypothesis which encompasses various aspects …
The Influence of Thiol Reagents on the Isoenzyme Pattern of Plant L+Lactate Dehydrogenase (EC 1.1.1.27)
1978
Summary Lactate dehydrogenase from potato tubers was incubated together with various thiol reagents and the effect on the electrophoretic behavior of its isoenzymes studied. while disulfides, alkylating agents, and H202 did not alter the number and electrophoretic behavior of the isoenzymes of L + LDH, reduced glutathione and 2-mercaptoethanol led to an increase in the number of isoenzymes. The reaction was dependent on concentration and pH. On the other hand, cysteine and cysteamine had no such effect. Results are discussed in view of the possible secondary nature of the plant LDH isoenzymes.
Regulation of Human Mitochondrial Aldehyde Dehydrogenase (ALDH-2) Activity by Electrophiles in Vitro
2011
Recently, mitochondrial aldehyde dehydrogenase (ALDH-2) was reported to reduce ischemic damage in an experimental myocardial infarction model. ALDH-2 activity is redox-sensitive. Therefore, we here compared effects of various electrophiles (organic nitrates, reactive fatty acid metabolites, or oxidants) on the activity of ALDH-2 with special emphasis on organic nitrate-induced inactivation of the enzyme, the biochemical correlate of nitrate tolerance. Recombinant human ALDH-2 was overexpressed in Escherichia coli; activity was determined with an HPLC-based assay, and reactive oxygen and nitrogen species formation was determined by chemiluminescence, fluorescence, protein tyrosine nitration,…
Interactions of silica nanoparticles with lung epithelial cells and the association to flotillins
2012
Amorphous silica nanoparticles (aSNPs) gain increasing popularity for industrial and therapeutic claims. The lung with its surface area of 100-140 m(2) displays an ideal target for therapeutic approaches, but it represents also a serious area of attack for harmful nanomaterials. The exact nature of the cytotoxic effects of NPs is still unknown. Furthermore, cellular pathways and the destiny of internalized NPs are still poorly understood. Therefore, we examined the cytotoxicity (MTS, LDH) and inflammatory responses (IL-8) for different-sized aSNPs (30, 70, 300 nm) on our lung epithelial cells line NCI H441 and endothelial cell line ISO-HAS-1. Additionally, colocalization studies have been c…
Triclosan induces Fas receptor-dependent apoptosis in mouse neocortical neurons in vitro
2014
Triclosan (TCS) is a commonly used antimicrobial agent in personal care and sanitizing products, as well as in household items. Numerous studies have demonstrated the presence of TCS in various human tissues. Several studies have reported the accumulation of TCS in fish and human brain tissue. The aim of the present study was to investigate the effect of TCS on apoptosis in mouse neocortical neurons after 7 days of culture in vitro following 3, 6 and 24 h of exposure. To explore the mechanism underlying the effects of TCS in neurons, we studied the activation and protein expression of the Fas receptor (FasR) and caspase- 8, caspase-9 and caspase-3, as well as DNA fragmentation in TCS-treate…
Effects of propanil on the European eel Anguilla anguilla and post-exposure recovery using selected biomarkers as effect criteria
2008
Abstract The aim of this study was to assess the physiological response of Anguilla anguilla to propanil and the degree of recovery after being moved to clean water. Preliminary acute toxicity test was carried out in the laboratory and the median lethal concentration (LC50) at 96 h was calculated as 31.33 mg/L (29.60–33.59 mg/L). NOEC and LOEC values (at 96 h) were also calculated as 20 and 25 mg/L, respectively. The fish were exposed to 0.63 and 3.16 mg/L of propanil for 72 h and allowed to recover for 144 h. Total proteins (TPs), γ -glutamil transpeptidase ( γ -GT), alanin aminotransferase (AlAT), alkaline phosphatase (AP), lactate dehydrogenase (LDH) and water content (WC) were assayed i…
In human endothelial cells rapamycin causes mTORC2 inhibition and impairs cell viability and function.
2008
Aim Drug-eluting stents are widely used to prevent restenosis but are associated with late endothelial damage. To understand the basis for this effect, we have studied the consequences of a prolonged incubation with rapamycin on the viability and functions of endothelial cells. Methods and results Human umbilical vein or aorta endothelial cells were exposed to rapamycin in the absence or in the presence of tumour necrosis factor α (TNFα). After a 24 h-incubation, rapamycin (100 nM) caused a significant cell loss associated with the increase of both apoptosis and necrosis, as quantified by propidium iodide staining, caspase 3 activity, and lactate dehydrogenase release. Rapamycin also impair…
Absence of malolactic activity is a characteristic of H+-ATPase-deficient mutants of the lactic acid bacterium Oenococcus oeni.
2003
ABSTRACT The lack of malolactic activity in H + -ATPase-deficient mutants of Oenococcus oeni selected previously was analyzed at the molecular level. Western blot experiments revealed a spot at 60 kDa corresponding to the malolactic enzyme only in the parental strain. Moreover, the mleA transcript encoding the malolactic enzyme was not detected by reverse transcription (RT)-PCR analysis of mutants. These results suggest that the malolactic operon was not transcribed in ATPase-deficient mutants. The mleR gene encoding a LysR-type regulatory protein which should be involved in expression of the malolactic genes was described previously for O. oeni . Results obtained in this study show that th…
Dihydroquercetin (DHQ) induced HO-1 and NQO1 expression against oxidative stress through the Nrf2-dependent antioxidant pathway.
2013
Dihydroquercetin (DHQ) is a well-known antioxidant agent. In the present investigation, we reported for the first time that DHQ stimulates the expression of phase II detoxifying enzymes through the Nrf2-dependent signaling pathway. The IC50 values of DHQ for reduction of 2,2-diphenyl-1-picrylhydrazol (DPPH), reducing power assay, lipid peroxidation assay, and xanthine oxidase inhibition were 5.96, 4.31, 2.03, and 13.24 μM, respectively. DHQ possessed considerable protective activity from oxidative DNA damage. A luciferase reporter assay also demonstrated that DHQ-activated signaling resulted in the increased transcriptional activity of Nrf2 through binding to the ARE (antioxidant response e…
Novel inhibitors of mitochondrial respiratory chain: endoperoxides from the marine tunicate Stolonica socialis.
2001
The Mediterranean tunicate Stolonica socialis contains a new class of powerful cytotoxic acetogenins, generically named stolonoxides. In this paper, which also details the isolation and chemical characterization of a minor component (3a) of the tunicate extract, we report the potent inhibitory activity (IC(50) < 1 microM) of stolonoxides (1a and 3a) on mitochondrial electron transfer. The compounds affect specifically the functionality of complex II (succinate:ubiquinone oxidoreductase) and complex III (ubiquinol:cytochrome C oxidoreductase) in mammalian cells, thereby causing a rapid collapse of the whole energetic metabolism. This result, which differs from the properties of similar known…