NADPH-cytochrome c reductase of Candida tropicalis grown on alkane.
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Alkanes↗
Biomedical subjects
E Azoulay
Publications and source records attributed to E Azoulay.
Hydroxylase regulation in Candida tropicalis grown on alkanes.
Candida tropicalis synthesizes a hydroxylase (3 to 5 nmol of product formed per minute per milligram of protein) and a cytochrome P-450 (0.10 to 0.13 nmol per milligram of protein) during growth on n-tetradecane. A three- to four-fold increase in the level of NADPH cytochrome c reductase is also observed in those cells as compared to the level of cells grown on glycerol. The most efficient inducers of the hydroxylase and of cytochrome P-450 are straight-chain alkanes having at least 10 carbon atoms. Alkenes and higher alcohols are also good inducers. There is little or no growth on ramified hydrocarbons such as pristane and on long-chain aldehydes and fatty acids. The partial inhibition of growth on decane is probably due to the denaturation of the microsomal electron carrier systems by the fatty acid formed by hydroxylation of the decane in the yeast.
Alkanes↗
Characterization of the membrane-bound nitrate reductase activity of aerobically grown chlorate-sensitive mutants of Escherichia coli K12.
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Aerobiosis↗
Characterization of an Escherichia coli K12 mutant that is sensitive to chlorate when grown aerobically.
Escherichia coli can normally grow aerobically in the presence of chlorate; however, mutants can be isolated that can no longer grow under these conditions. We present here the biochemical characterization of one such mutant and show that the primary genetic lesion occurs in the ubiquinone-8-biosynthetic pathway. As a consequence of this, under aerobic growth conditions the mutant is apparently unable to synthesize formate dehydrogenase, but can synthesize a Benzyl Viologen-dependent nitrate reductase activity. The nature of this activity is discussed.
Acridines↗
Methaemoglobinemia induced by nitric oxide in whole blood. Quantitative relationship.
We studied in vitro the effects of nitric oxide (NO) in human and rat blood and in human erythrolysate. Using NO in the tonometric technique allows to predict through an experimental model the amount of methemoglobin formed. At known oxygen and carbon dioxide pressures, methaemoglobinemia is all the more important as NO concentration is great and tonometry duration is long. Moreover methaemoglobin concentration is greater in saturated (P02 congruent to 500 Torr) than in desaturated blood (P02 congruent to O Torr) while only slight changes occur for small P02 variations. Thus the study of the oxygen dissociation curve should be possible in presence of NO. Methaemoglobin is responsible for the drop in the oxygen combining capacity and thus impairs blood oxygen transport. Results are similar in human and in rat blood.
Animals↗
Participation of cytochrome b to the in-vitro reconstitution of the membrane-bound formate-nitrate reductase of Escherichia coli K 12 and the possible role of sulfhydryl groups and temperature in the reconstitution process.
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Aldehyde Oxidoreductases↗
Oxidative phosphorylation in intact chl-r mutants of Escherichia coli K 12.
The efficiency of oxidative phosphorylation was estimated in intact resting cells of Escherichia coli K 12, strain PA 601 (chl-s) and its chl-r mutants, all of them grown anaerobically in the presence of nitrate. The oxidation of endogenous NADH in intact chl-s cells was accompanied by the formation of ATP whatever the terminal electron acceptor, oxygen or nitrate, so that it was possible to conclude that the energy conservation sites are operating with either of the two acceptors in cells grown anaerobically in the presence of nitrate. For chl-r mutants oxidation of endogenous NADH correlated with ATP-production was found only with oxygen as electron acceptor. It is concluded that the energy-conservation sites are preserved in these mutants, the nitrate respiratory chain of which is altered. This assumption is corroborated by the effects of uncouplers of oxidative phosphorylation on ATP-synthesis.
Aerobiosis↗
[Ultrastructure of the particles reconstituted by complementation of extracts from chl-r mutants of Escherichia coli K 12].
By freeze-fracturing it is shown that the vesicles reconstituted by complementation of the chlA and chlB mutants of E. coli K 12 extracts are characterized by an asymmetric membrane bilayer. In a feature quite similar to the original intact plasma membranes, the membrane splits in two halves and the intramembranous particles are asymmetrically distributed on the two facture faces. It is proposed that the process of membrane reconstitution, which is also associated with the restoration of nitrate-reductase activity, relies on a sequence of increasing complexity of the molecular organisation.
Adenosine Triphosphatases↗
Microsomal cytochromes of Candida tropicalis grown on alkanes.
A comparison of methods used in isolating microsomes and in measuring microsomal cytochrome P-450 demonstrated that separation following protoplast lysis gave the best results. By this latter technique a high amount of cytochrome P-450 (0.2-0.3 nmol/mg) was recovered but cytochrome P-420, considered as the denatured form, was absent. The alkanes specifically induce cytochromes P-450 and b5 localized on the microsomes. The denaturation in vivo of cytochrome P-450 into cytochrome P-420 even occurs during storage at 1 degree C. This degradation is increased during preparation of subcellular fractions if no preventive measures are taken.
Alkanes↗
[Hydrocarbon metabolism in a marine bacterium].
The marine bacterium L.16.1 (Alcaligenes sp.) grows preferentially on alkanes (C10 to C18) with a very high growth yield (98 per cent); optimal growth depends strictly on the presence of a well-defined NaCl concentration (100 mM). Our strain is constitutive for the enzymatic systems responsible for the oxidation of alkanes to fatty acids, i.e. NADH-dependent hydroxylase, alcohol and aldehyde dehydrogenases, the latter of which located at the cytoplasmic membrane level. The aerobic oxidation of primary alcohols by particulate extracts prepared in the presence of 400 mM NaCl is NAD+-dependent (Km = 0.082 mM, Vmax = 238 with decanol). With extracts prepared in the absence of NaCl, Vmax undergoes a very strong decrease. On the contrary , the NAD+ (P)+-dependent oxidation of aldehydes is carried out anaerobically by the same extracts irrespective of the presence or the absence of added Na+ in the solutions used for the preparation of these extracts. A possible explanation for our results could be that Na+ acts on the enzymatic systems for which the maintenance of the membrane integrity is essential. This interpretation is consistent with the slowing down of the growth speed accompanying the decrease of NaCl concentration in the growth medium. With regard to alcohol and aldehyde-dehydrogenases, it is noteworthy that these enzymes behave like similar enzymatic activities induced by alkanes in other microorganisms.
Alcaligenes↗
[Demonstration of 2 phosphate transport systems in Candida tropicalis].
Candida tropicalis has two phosphate transport systems, one of which is constitutive and has a low affinity for its substrate (Kmapp 1.2.10(-3) M). The other one characterized by a high affinity for H2PO4- (Kmapp = 4.5.10(-6) M) appears only under phosphate starvation conditions. The regulation of the latter would act on the one hand on the synthesis of binding proteins for P1 (repression-derepression) and on the other on the activation or inactivation of the carriers.
Binding Sites↗
[Isolation and study of a new marine bacterium growing on hydrocarbons. I. Physiological study (author's transl)].
The bacterial strain L.16.1 isolated from coastal waters polluted by oil-waste, close to the genus Alcaligenes, utilizes preferentially alkanes with a carbon number greater than 9. Sugars and amino-acids cannot serve as carbon source to this bacterium. Cells grown on hydrocarbon the chain length of which ranges from C10 to C18 exhibit very high yield (98%) with a growth rate of 0.47. From our studies it appears that strain L.16.1 is strictly dependent on the presence of the Na+ ion and that this Na+ dependence can be seen at each level of the physiological activity. Alkane-grown cells show morphological features namely disc shaped cytoplasmic vesicles (6-8 per cell). Such vesicles are to be regarded as a consequence of the very high lipid content (twice the standard) which characterizes these cells. Additional lipids belong essentially to the nonsaponifiable fraction (20 times more in hexadecane grown cells); on the contrary, the phospholipid content at both qualitative and quantitative points of view does not depend on the nature of the growth substrate.
Alcaligenes↗
[Isolation and study of a new marine bacterium growing on hydrocarbons. II. Mechanism of lysis and viability (author's transl)].
The growth of the marine bacterium (L.16.1) is strictly dependent on the presence of well-defined NaCl concentrations (100 mM on alkanes and 75 mM on acetate, pyruvate or propionate) in the medium. L.16.1 cells undergo lysis on transfer from high to low ionic environment. This lytic phenomenon, which can be prevented by the presence of Na+ or divalent cations, appears to be due to the loss of Mg++ and Ca++ by the cells. Evidence for this hypothesis is provided by the assays of intracellular and extracellular Na+, K+, Mg++ and Ca++ concentrations. The maintenance of the cell integrity of the organism does not depend on the medium osmolarity, since osmotic compounds such as sucrose, glycerol or mannitol cannot prevent lysis. All of the ions which can maintain the cell integrity are not likewise able to keep viability; this has been found to be a function of Na+ concentration (70% survival after 24 hours in 400 mM NaCl, only 10% in 50 mM MgSO4).
Alcaligenes↗
[Isolation and study of a new marine bacterium growing on hydrocarbons. III. Oxidation of substrates and effects of detergents on the cells (author's transl)].
The oxidation of exogenous hexadecane by cells of strain L.16.1 is a function of intracellular and extracellular Na+ and K+ concentrations. The cells which lost their Na+ as a result of washing in the absence of sodium chloride oxidize hexadecane at a very low rate. Washings in the absence of Mg++ and Ca++ do not result in a similar decrease of the respiratory activity. The latter cannot be maintained--or restored after decrease--by the divalent cations which are active in preventing cytolysis (see the preceding paper). A possible explanation for this Na+ dependence could lie in a particular role played by Na+ inthe cytoplasmic membrane and in some function related to the oxidative activities of the cell membrane. From other studies carried out with ionic detergents it was observed that growth and respiratory activity are inhibited by very low concentrations of these compounds contrary to non ionic detergents which can serve as growth substrates and are oxidized like hexadecane or acetate. It is concluded that the bulk of our results could best be accounted by assuming that the membranes of halophilic bacteria are organized according to a specific organization scheme.
Alcaligenes↗
Lack of effect of methemoglobinemia on the plasma-erythrocyte pH relationship.
A stable and reproducible methemoglobinemia is induced by small concentration of an oxidizing gas (NO). Under such conditions we evidenced that plasma pH (pHe) to erythrocyte pH (pHi) relationship is unchanged. A strong acidity bound to the changes of NO in water occurs. But we may conclude that the buffer capacity of erythrocyte is not modified by the oxydation of ferro into ferrihemoglobin within the erythrocyte.
Acid-Base Equilibrium↗
Blood affinity for oxygen in experimental hemorrhagic shock with metabolic acidosis.
This study was designed to evaluate, in vivo, the effect of a severe non-respiratory acidosis on hemoglobin oxygen transport. Oxygen affinity of hemoglobin, Bohr effect, Hill's number and red cell 2,3-DPG were evaluated during experimental hemorrhagic shock in dogs. Three periods were considered: control, hypotension (mean arterial pressure 60 mm Hg for 2 hr 30 min) and blood replacement. There was no significant change in erythrocyte 2,3-DPG following hemorrhagic hypotension but ATP increased significantly. n, the Hill number (2.6), was not changed by in vivo acidosis (pH 7.1). Respiratory Bohr coefficient (BCO2) corresponding to pHe variations was drastically reduced (control BCO2 = 0.55, acidosis BCO2 = 0.31, blood replacement BCO2 = 0.35). P50(7.4) was not modified significantly by hemorrhagic acidosis. It is unlikely that variations of blood affinity for oxygen play a major role in oxygen delivery during early experimental hemorrhagic shock.
Acidosis↗
Oxygen transport by haemoglobin. A comparison of whole blood, washed erythrocytes and haemoglobin solution.
The properties of haemoglobin oxygen transport were compared under three different conditions: red cell in its natural medium, i.e. plasma (whole blood), washed red cell and haemoglobin A, the former suspended, the latter solved in an iso-osmotic tris buffer. The oxygen haemoglobin affinity (expressed as P50) and the respiratory Bohr effect variations were studied with modified media and unchanged pH and 2,3-diphosphoglycerate (2,3-DPG) concentration. Provided they are refered to intra-erythrocytic pH, none of these values were changed when varying environment. These results suggest that the three major ligands (H+ ions, 2,3-DPG and CO2) interaction with haemoglobin is largely predominant upon other factors which would interfere, and can completely account for oxygen transport by haemoglobin.
Diphosphoglyceric Acids↗
Effect of concanavalin A on membrane-bound enzymes from mouse lymphocytes.
The ionic influence and ouabain sensitivity of lymphocyte mg-2+-atpase and Mg-2+-(Na+ +K+)-activated ATPase were studied in intact cells, microsomal fraction and isolated plasma membranes. The active site of 5'-nucleotidase and Mg2+-ATPase seemed to be localized on the external side of the plasma membrane whereas the ATP binding site of (Na+ +K+)-ATPase was located inside the membrane. Concanavalin A induced an early stimulation of Mg2+-APTase and (Na+ +K+)-ATPase both on intact cells and purified plasma membranes. In contrast, 5'-nucleotidase activity was not affected by the mitogen. Although the thymocyte Mg2+-ATPase activity was 3-5 times lower than in spleen lymphocytes, it was much more stimulated in the former cells (about 40 versus 20%). (Na+ +K+)-ATPase activity was undectectable in thymocytes. However, in spleen lymphocytes (Na+ +K+)-ATPase activity can be detected and was 30% increased by concanavalin A. Several aspects of this enzymic stimulation had also characteristic features of blast transformation induced by concanavalin A, suggesting a possible role of these enzymes, especially Mg2+-ATPase, in lymphocyte stimulation.
Adenosine Triphosphatases↗