scholarly journals The effect of inhibitors on the oxygen kinetics of terminal oxidases of Acanthamoeba castellanii

1979 ◽  
Vol 182 (1) ◽  
pp. 11-15 ◽  
Author(s):  
D Lloyd ◽  
S Edwards ◽  
B Kristensen ◽  
H Degn
Keyword(s):  
Competitive Inhibition ◽  
Acanthamoeba Castellanii ◽  
Exponential Phase ◽  
Oxygen Utilization ◽  
Late Exponential Phase ◽  
Salicylhydroxamic Acid ◽  
Terminal Oxidases ◽  
Low Concentrations ◽  
Transport Chain ◽  
Oxygen Sensitive

1. Respiration of growing cultures of Acanthamoeba castellanii is inhibited less than 60% by azide (35 mM); the respiration of early-exponential-phase cultures differs from that of late-exponential-phase cultures in being stimulated by up to 120% by low concentrations (less than 1 mM) of this inhibitor. Azide (0.5 mM) plus 1 mM-salicylhydroxamic acid gives 80% inhibition of respiration in early- or late-exponential-phase cultures. 2. Lineweaver-Burk plots of 1/v against 1/[O2] for growing and stationary-phase cultures give values of less than 1 muM for the apparent Km for oxygen. 3. These values are not significantly altered when determined in the presence of 1 mM-salicylhydroxamic acid. 4. Higher values (greater than 7 muM) for apparent Km values for oxygen were obtained in the presence of azide, which gives non-linear Lineweaver-Burk plots. 5. Competitive inhibition of respiration by CO occurs with Ki 2.4 muM. 6. The results are discussed in terms of the presence of three terminal oxidases in this organism, namely two oxidases with high affinities for oxygen (cytochrome c oxidase of the main phosphorylating electron-transport chain and the salicylhydroxamic acid-sensitive oxidase) and a third oxidase with a low affinity for oxygen, sensitive to inhibition by cyanide but not by azide or salicylhydroxamic acid. The relative contributions to oxygen utilization by these oxidases change during the growth of a batch culture.

Biodegradation rates of aromatic contaminants in biofilm reactors

1995 ◽  
Vol 31 (1) ◽  
pp. 117-128 ◽  
Author(s):  
Jean-Pierre Arcangeli ◽  
Erik Arvin
Keyword(s):  
Aromatic Hydrocarbons ◽  
Competitive Inhibition ◽  
Removal Rate ◽  
First Order ◽  
Biofilm Reactors ◽  
First Order Kinetics ◽  
Reducing Conditions ◽  
Low Concentrations ◽  
Degradation Rates ◽  
Order Surface

This study has shown that microorganisms can adapt to degrade mixtures of aromatic pollutants at relatively high rates in the μg/l concentration range. The biodegradation rates of the following compounds were investigated in biofilm systems: aromatic hydrocarbons, phenol, methylphenols, chlorophenols, nitrophenol, chlorobenzenes and aromatic nitrogen-, sulphur- or oxygen-containing heterocyclic compounds (NSO-compounds). Furthermore, a comparison with degradation rates observed for easily degradable organics is also presented. At concentrations below 20-100 μg/l the degradation of the aromatic compounds was typically controlled by first order kinetics. The first-order surface removal rate constants were surprisingly similar, ranging from 2 to 4 m/d. It appears that NSO-compounds inhibit the degradation of aromatic hydrocarbons, even at very low concentrations of NSO-compounds. Under nitrate-reducing conditions, toluene was easily biodegraded. The xylenes and ethylbenzene were degraded cometabolically if toluene was used as a primary carbon source; their removal was influenced by competitive inhibition with toluene. These interaction phenomena are discussed in this paper and a kinetic model taking into account cometabolism and competitive inhibition is proposed.

Ferrous iron oxidation in moderately thermophilic acidophile Sulfobacillus sibiricus N1T

2010 ◽  
Vol 56 (10) ◽  
pp. 803-808 ◽  
Author(s):  
Tatiana Y. Dinarieva ◽  
Anna E. Zhuravleva ◽  
Oksana A. Pavlenko ◽  
Iraida A. Tsaplina ◽  
Alexander I. Netrusov
Keyword(s):  
Ferrous Iron ◽  
High Performance ◽  
Iron Oxidation ◽  
Early Exponential Phase ◽  
Moderately Thermophilic ◽  
Terminal Oxidases ◽  
Cytochrome Bo ◽  
Ferrous Iron Oxidation ◽  
Transport Chain ◽  
Membrane Bound

The iron-oxidizing system of a moderately thermophilic, extremely acidophilic, gram-positive mixotroph, Sulfobacillus sibiricus N1T, was studied by spectroscopic, high-performance liquid chromatography and inhibitory analyses. Hemes B, A, and O were detected in membranes of S. sibiricus N1T. It is proposed that the electron transport chain from Fe2+ to O2 is terminated by 2 physiological oxidases: aa3-type cytochrome, which dominates in the early-exponential phase of growth, and bo3-type cytochrome, whose role in iron oxidation becomes more prominent upon growth of the culture. Both oxidases were sensitive to cyanide and azide. Cytochrome aa3 was more sensitive to cyanide and azide, with Ki values of 4.1 and 2.5 µmol·L–1, respectively, compared with Ki values for cytochrome bo3, which were 9.5 µmol·L–1 for cyanide and 7.0 µmol·L–1 for azide. This is the first evidence for the participation of a bo3-type oxidase in ferrous iron oxidation. The respiratory chain of the mixotroph contains, in addition to the 2 terminal oxidases, a membrane-bound cytochrome b573.

scholarly journals The oxidation of nicotinic acid by Pseudomonas ovalis Chester. The terminal oxidase

1972 ◽  
Vol 129 (3) ◽  
pp. 755-761 ◽  
Author(s):  
M. V. Jones ◽  
D. E. Hughes
Keyword(s):  
Electron Transport ◽  
Nicotinic Acid ◽  
Electron Transport Chain ◽  
Acid Oxidase ◽  
Terminal Oxidase ◽  
Difference Spectra ◽  
Terminal Oxidases ◽  
Cytochrome O ◽  
Transport Chain ◽  
Terminal Oxidation

In cell-free extracts of Pseudomonas ovalis nicotinic acid oxidase is confined to the wallmembrane fraction. It is associated with an electron-transport chain comprising b- and c-type cytochromes only, differing proportions of which are reduced by nicotinate and NADH. CO difference-spectra show two CO-binding pigments, cytochrome o (absorption maximum at 417nm) and another component absorbing maximally at 425nm. Cytochrome o is not reduced by NADH or by succinate but is by nicotinate, which can also reduce the ‘425’ CO-binding pigment. The effects of inhibitors of terminal oxidation support the idea of two terminal oxidases and a scheme involving the ‘425’ CO-binding pigment and the other components of the electron-transport chain is proposed.

Response of Liverwort Cells to Peroxidizing Herbicides

1992 ◽  
Vol 47 (5-6) ◽  
pp. 394-399
Author(s):  
Shuji Iwata ◽  
Naoko Nakayama ◽  
Shunji Nakagawara ◽  
Yoshimoto Ohta ◽  
Takaharu Tanaka ◽  
...  
Keyword(s):  
Cell Growth ◽  
Oxidative Damage ◽  
Early Treatment ◽  
Protoporphyrin Ix ◽  
Cell Suspension Cultures ◽  
Exponential Phase ◽  
Marchantia Polymorpha ◽  
Late Exponential Phase ◽  
Kinetics Of

Cell suspension cultures of the liverwort, Marchantia polymorpha L. were found useful to study the influence of peroxidizing herbicides either on the greening process or on the fully green cells. The cells of both physiological stages exhibit a characteristic sensitivity to the herbicides. The sensitivity increased rapidly during the exponential phase of growth, reached a maximum during the late exponential phase, and then decreased in the stationary phase. We investigated the kinetics of accumulation of protoporphyrin IX (PPIX) in Marchantia cells treated with several peroxidizing herbicides at various stages of cell growth, and observed a correlation between accumulation of PPIX and herbicidal damage. The glutathione (GSH) content in the cell was also investigated to examine the role of GSH against herbicide treatment. In the light, GSH levels in the cells treated with AFM rose rapidly reaching a peak after 8 h, and rapidly decreased subsequently. The beginning of PPIX accumulation coincided with the decline of GSH after 8 h of treatment. Obviously, GSH plays a key role in protection against oxidative damage caused by AFM in the early treatment period. In the dark, AFM also induced an accumulation of GSH and PPIX, followed by a decline in GSH and PPIX contents during a 20 h incubation. The decline of PPIX was observed several hours after GSH starts to decrease, remaining at a constant level for the following 40 h, leading to accumulation of an other fluorescent still-unknown pigment.

A new CCK analogue differentiates two functionally distinct CCK receptors in rat and mouse pancreatic acini

1989 ◽  
Vol 257 (4) ◽  
pp. G594-G600 ◽  
Author(s):  
T. Matozaki ◽  
J. Martinez ◽  
J. A. Williams
Keyword(s):  
Competitive Inhibition ◽  
Inhibitory Effect ◽  
Leucine Incorporation ◽  
Amylase Release ◽  
Pancreatic Acini ◽  
Cck Receptors ◽  
Partial Agonists ◽  
Low Concentrations ◽  
Phenylalanine Residue ◽  
Stimulation Of

Analysis of the competitive inhibition of 125I-labeled cholecystokinin octapeptide (CCK-8) binding to isolated rat or mouse pancreatic acini showed that in both species CCK-8 interacts with two different affinity sites. A newly synthesized CCK analogue modified at the COOH-terminal phenylalanine residue totally inhibited 125I-CCK binding. This interaction occurred with sites of a single affinity in rat acini but with two different affinity sites in mouse acini. When acini were incubated with increasing concentrations of CCK-8, a biphasic stimulation of amylase release was observed. By use of rat acini, the analogs stimulated amylase release but caused no inhibition at supramaximal concentrations. By contrast, in mouse pancreatic acini, analogues showed a biphasic stimulation of amylase release similar to CCK-8. Both CCK-8 and the analogue stimulated [3H]leucine incorporation into protein at low concentrations in rat pancreatic acini. Higher concentrations of CCK-8 profoundly inhibited [3H]leucine incorporation, whereas the analogue had no inhibitory effect. Moreover, the analogue at higher concentrations blocked the inhibition of [3H]leucine incorporation caused by CCK-8 but did not affect carbamylcholine-induced inhibition. In mouse acini, however, the CCK analogue inhibited [3H]leucine incorporation similar to the effect of CCK-8. The results support the concept that occupancy of distinct affinity sites or states of the CCK receptor is associated with specific biological actions. A model of the CCK receptor is proposed in which two interchangeable affinity states exist. By occupying all the receptors in only one state, the new CCK analogues serve as partial agonists of some and antagonists of other actions of CCK.

scholarly journals The mannophosphoinositides of Corynebacterium aquaticum

1975 ◽  
Vol 148 (2) ◽  
pp. 253-258 ◽  
Author(s):  
J A Hackett ◽  
P J Brennan
Keyword(s):  
Stationary Phase ◽  
Exponential Growth ◽  
Growth Cycle ◽  
Exponential Phase ◽  
Late Stationary Phase ◽  
Late Exponential Phase

Besides the monomannophosphoinositide previously reported in Corynebacterium aquaticum small amounts of other, apparently more glycosylated, mannophosphoinositides have been identified in stationary phase cells. Moreover, by labelling cells with [32P]Pi, phosphatidylinositol was found, comprising about 1.5% of the stationary-phase phospholipids. 2. Pulse-chase experiments performed on cells in the late exponential phase of growth further suggested the sequence phosphatidylinositol leads to monomannophosphoinositide as the first step in the biosynthesis of the mannophosphoinositides. 3. Di-and tri-mannophosphoinositides are apparently the main mannophosphoinositides present during exponential growth. Monomannophosphoinositide predominates only in late stationary phase; in the earlier stationary phase, phosphatidylinositol comprises 50% of the phosphoinositide lipid, and tetramannophosphoinositide constitutes much of the remainder. 4. The metabolism and functions of the mannophosphoinositides are discussed, particularly in relation to changes in their composition throughout the growth cycle.

scholarly journals Endothelin-Induced Contraction and Relaxation of Rat Isolated Basilar Artery: Effect of BQ-123

1994 ◽  
Vol 14 (5) ◽  
pp. 845-852 ◽  
Author(s):  
G. I. Feger ◽  
L. Schilling ◽  
H. Ehrenreich ◽  
M. Wahl
Keyword(s):  
Nitric Oxide ◽  
Basilar Artery ◽  
Competitive Inhibition ◽  
Regression Curve ◽  
Low Concentrations ◽  
Small Contraction ◽  
The Right ◽  
Contraction And Relaxation ◽  
Oxide Synthase ◽  
Concentration Response Curve

In ring segments from rat basilar artery (BA) the endothelin (ET) peptides ET-1, ET-2, and ET-3 induced concentration-related contractions. The order of potency was ET-1 = ET-2 > ET-3, while no differences occurred in the maximum contraction. The selective ETA receptor antagonist, BQ-123 (10−10-10−4 M) alone elicited a small contraction only at 10−4 M. In the presence of BQ-123 (10−7-10−5 M), the concentration-response curve for ET-1 was shifted to the right without any decrease in maximum contraction, indicating competitive inhibition of ET-1 binding to the ETA receptor by BQ-123. The pA2 value calculated for BQ-123 was 6.935; the slope of the regression curve was 0.734. In contrast to ET-1, the contractile action of ET-3 was abolished by 10−5 M BQ-123. In segments precontracted with 10−6 M serotonin, ET-3, but not ET-1, induced relaxation at low concentrations (10−11-10−8 M), with maximum relaxation amounting to 17.8 ± 14.7% of precontraction (mean ± SD; n = 16). The relaxant action of ET-3 was abolished in vessels incubated with NG-nitro-l-arginine (10−5 M), an inhibitor of nitric oxide synthase. These results indicate that the ET-induced contraction of the isolated rat BA involves activation of the ETA receptor. The ET-3-induced relaxation of precontracted rat BA is apparently mediated by release of nitric oxide from the endothelium.

scholarly journals Cyanide-insensitive oxidation of ascorbate + NNN′N′-tetramethyl-p-phenylenediamine mixture by mung-bean (Phaseolus aureus) mitochondria. An energy-linked function

1978 ◽  
Vol 176 (1) ◽  
pp. 129-136 ◽  
Author(s):  
S B Wilson
Keyword(s):  
Oxygen Uptake ◽  
Mung Bean ◽  
Electron Flow ◽  
Plant Mitochondria ◽  
Phosphorylation Site ◽  
Antimycin A ◽  
Phaseolus Aureus ◽  
Salicylhydroxamic Acid ◽  
Low Concentrations ◽  
High Concentrations

Freshly prepared washed or purified mung-bean (Phaseolus aureus) mitochondria utilize oxygen with ascorbate/tetramethyl-p-phenylenediamine mixture as electron donor in the presence of KCN. ATP control of the oxygen uptake can be observed with very fresh mitochondria. The electron flow, which is inhibited by antimycin A, salicylhydroxamic acid or octylguanidine, takes place by reversed electron transport through phosphorylation site II and thence to oxygen through the cyanide-insensitive pathway. Oligomycin and low concentrations of uncoupler partially inhibit the oxygen uptake in a manner similar to that observed for other energy-linked functions of plant mitochondria. An antimycin A-insensitive oxygen uptake occurs if high concentrations of uncoupler are used, indicating that the pathway of electron flow has been altered. The process of cyanide-insensitive ascorbate oxidation is self-starting, and, since it occurs in the presence of oligomycin, it is concluded that the reaction can be energized by a single energy-conservation site associated with the cyanide-insensitive oxidase pathway.

scholarly journals Incorporation of [14C]shikimate into phenazines and their further metabolism by Pseudomonas phenazinium

1977 ◽  
Vol 164 (1) ◽  
pp. 139-145 ◽  
Author(s):  
Graham S. Byng ◽  
John M. Turner
Keyword(s):  
Culture Media ◽  
Kinetic Studies ◽  
Exponential Phase ◽  
Late Exponential Phase ◽  
Pigment Formation ◽  
Naturally Occurring ◽  
Common Precursor ◽  
The Common

1. During growth of Pseudomonas phenazinium on l-threonine medium, phenazine pigment formation commenced early and 1,6-dihydroxyphenazine 5,10-dioxide (iodinin) was the major component. Growth on l-[U-14C]threonine showed that when growth was complete about 25% of the label had been incorporated into phenazines and 30% into cell substance. 2. The addition of d-[2,3,4,5(n)-14C]shikimate to cultures at different phases of growth showed that the greatest efficiency of incorporation (about 70%) occurred in the mid- to late-exponential phase. Phenazines accounting for most of the 14C supplied were iodinin and 9-hydroxyphenazine-1-carboxylate plus 2,9-dihydroxyphenazine-1-carboxylate. Radioactivity incorporated into cell substance was about one-third of the amount found in phenazines. 3. Kinetic studies showed that radioactivity from a pulse of [14C]-shikimate was incorporated into phenazines immediately, without a discernible lag, and into all detectable phenazines simultaneously rather than sequentially. 4. Radioactive phenazines isolated from culture media were fed to growing cultures and their metabolism was studied. The results supported a scheme for the biosynthesis of iodinin and 1,8-dihydroxyphenazine 10-monoxide by a branched pathway. 5. It is proposed that phenazine-1,6-dicarboxylate is the common precursor of all naturally occurring phenazines.

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