Search results for "ATP synthase"

Inhibitory responses to exogenous adenosine in murine proximal and distal colon

2006

The aims of the present study were firstly, to characterize pharmacologically the subtypes of P(1) purinoreceptors involved in the inhibitory effects induced by exogenous adenosine in longitudinal smooth muscle of mouse colon, and secondly, to examine differences in the function and distribution of these receptors between proximal and distal colon. Adenosine (100 microM-3 mM) caused a concentration-dependent reduction of the amplitude of spontaneous contractions in the proximal colon, and muscular relaxation in the distal colon. In the proximal colon, adenosine effects were antagonized by a selective A(1) receptor antagonist, 1,3-dipropyl-8-cyclopentylxanthine (DPCPX, 10 nM), but were not m…

Control of oxidative metabolism in volume-overloaded rat hearts: effects of different lipid substrates.

1994

The relationship between intracellular energy parameters and myocardial O2 consumption (VO2) was studied in control and volume-overloaded hearts perfused with different lipid substrates and over a range of left ventricular work loads. In control hearts, a unique linear relationship between log of cytosolic [ATP]/[ADPf].[Pi] (where [ADPf] is concentration of free ADP) and myocardial VO2 was observed between low and high work loads for both fatty acids studied. In volume-overloaded hearts perfused in the presence of exogenous palmitate, the slope of the relationship between log [ATP]/[ADPf].[Pi] and myocardial VO2 was considerably depressed. It would seem that, under these conditions, much o…

Vinorine synthase from Rauvolfia: the first example of crystallization and preliminary X-ray diffraction analysis of an enzyme of the BAHD superfamily

2004

Abstract Crystals of vinorine synthase (VS) from medicinal plant Rauvolfia serpentina expressed in Escherichia coli have been obtained by the hanging-drop technique at 305 K with ammonium sulfate and PEG 400 as precipitants. The enzyme is involved in the biosynthesis of the antiarrhythmic drug ajmaline and is a member of the BAHD superfamily of acyltransferases. So far, no three-dimensional structure of a member of this enzyme family is known. The crystals belong to the space group P 2 1 2 1 2 1 with cell dimensions of a =82.3 A, b =89.6 A and c =136.2 A. Under cryoconditions (120 K), a complete data set up to 2.8 A was collected at a synchrotron source.

A study on 3‐deoxy‐D‐arabino‐heptulosonic Acid 7‐Phospate Synthase in Higher Plants. The existence of three isoenzymes in Pisum sativum

1976

Purification and partial amino acid sequences of the enzyme vinorine synthase involved in a crucial step of ajmaline biosynthesis.

2004

The acetyl-CoA-dependent enzyme vinorine synthase was isolated from hybrid cell suspension cultures of Rauvolfia serpentina and Rhazya stricta. The sarpagan-type alkaloid gardneral was used as a substrate of the enzyme leading to the ajmalan-type 10-methoxyvinorine. An HPLC-based assay was developed to monitor vinorine synthase activity, which allowed establishing a five step purification procedure combining anion exchange, hydrophobic interaction, hydroxyapatite and gel filtration. Purification resulted in a yield of 0.2% and an approximately 991-fold enrichment of the acetyltransfer activity. SDS-PAGE analysis showed a Mr for the enzyme of approximately 50 kDa. The four peptide fragments …

Light-induced proton slip and proton leak at the thylakoid membrane

2005

A treatment of leaves of Spinacia oleracea L. with light or with the thiol reagent dithiothreitol in the dark led to partly uncoupled thylakoids. After induction in intact leaves, the partial uncoupling was irreversible at the level of isolated thylakoids. We distinguish between uncoupling by proton slip, which means a decrease of the H+/e(-) -ratio due to less efficient proton pumping, and proton leak as defined by enhanced kinetics of proton efflux. Proton slip and proton leak made about equal contributions to the total uncoupling. The enhanced proton efflux kinetics corresponded to reduction of subunit CF1-gamma of the ATP synthase as shown by fluorescence labeling of thylakoid proteins …

Crystallization and preliminary X-ray analysis of native and selenomethionyl vinorine synthase from Rauvolfia serpentina.

2005

Vinorine synthase (VS) is a central enzyme of the biosynthesis of the antiarrhythmic drug ajmaline and is a member of the BAHD superfamily of acyltransferases. So far, no three-dimensional structure with significant sequence homology with VS is known. Crystals of VS and selenomethionyl-labelled VS from the medicinal plant Rauvolfia serpentina have been obtained by the hanging-drop technique at 305 K with ammonium sulfate and PEG 400 as precipitants. VS crystals diffract to 2.8 Å and belong to space group P212121, with unit-cell parameters a = 82.3, b = 89.6, c = 136.2 Å. The selenomethionyl VS crystal was nearly isomorphous with the VS crystal.

Incorporation of ATP synthetase into long-term stable liposomes of a polymerizable synthetic sulfolipid

1981

Subcellular localization and characterization of nitric oxide synthase(s) in endothelial cells: physiological implications.

1994

Endothelial cells (EC) contain a constitutive Ca2+/calmodulin-dependent nitric oxide (NO) synthase (cNOS) which plays an important role in the local control of vascular tone. We compared the subcellular distribution of this enzyme in cultured and freshly isolated pig EC by determination of specific cNOS activity and immunoblot analysis. Similar studies were also performed with cultured and freshly isolated bovine and cultured human EC. Enzyme activity was predominantly (> 70%) associated with the particulate fraction of all EC types tested and was highest in freshly isolated porcine EC. Both specific cNOS activity and immunoreactivity were substantially higher (> 3-fold) in th…

Trichinella spiralisThymidylate Synthase: Developmental Pattern, Isolation, Molecular Properties, and Inhibition by Substrate and Cofactor Analogues

1996

Abstract Thymidylate synthase specific activity was found to remain at a constant level in crude extracts from muscle larvae, isolated (1-15 months after infection) by pepsin-HCl digestion, as well as from adult worms ofTrichinella spiralis.The enzyme was purified and its molecular (monomer mol. wt 35 kD) and kinetic (sequential mechanism with the Kmvalues 3.1 and 19 μM for dUMP and N5,10-methylenetetrahydrofolate, respectively) properties determined. 5-Fluoro-dUMP was a competitive, slow-binding inhibitor of the parasite enzyme. N5,10-methylenetetrahydrofolate analogues 10-propargyl-5,8-dideazafolate (CB3717), ZD1694, BW1843U89, and AG337 were weaker inhibitors of the parasite than regener…