Activation of mitochondrial fatty acid oxidation by calcium. Conversion to the energized state.
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Adenosine Triphosphate↗
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[Cyclic pathway of formaldehyde oxidation in Pseudomonas oleovorans].
Operation of the dissimilatory hexulose phosphate cycle of formaldehyde oxidation in Pseudomonas oleovarans has been directly confirmed. Extracts of this typical facultative methylotroph catalyze the formation of 14CO2 from 14C-formaldehyde. The process depends on the presence of ribose-5-phosphate, NADP or NAD, and is linear in time. Oxidation of formaldehyde via formate to CO2 is of a minor importance in the energy metabolism of the methylotroph.
Formaldehyde↗
[Nicotinamide coenzymes at the early stages of light induction of carotenogenesis in the Neurospora crassa mycelium].
Changes in the concentration of NAD+, NADH, NADP+ and NADPH in the mycelium of the NADase free mutant of Neurospora crassa were studied during the latent stage of light induction of carotenogenesis. A 30 minute illumination by visible light brought about a stable decrease in the NADH/NAD+NADH ratio, exerting no effect on the NADPH/NADP+NADPH ratio. At the same time the NADP+/NAD+ ratio increased. These changes occurred only when illumination induced carotenoid accumulation in the N. crassa mycelium.
Carotenoids↗
Determination of the molar absorptivity of NADH.
The molar absorptivity of NADH at 340 nm has been determined by an indirect procedure in which high-purity glucose is phosphorylated by ATP in the presence of hexokinase, coupled to oxidation of the glucose-6-phosphate by NAD+ in the presence of glucose-6-phosphate dehydrogenase. The average value from 85 independent determinations is 6317 liter mol-1 cm-1 at 25 degrees C and pH 7.8. The overall uncertainty is -4.0 to +5.5 ppt (6292 to 6352 liter mol-1 cm-1), based on a standard error of the mean of 0.48 ppt and an estimate of systematic error of -2.6 to +4.1 ppt. Effects of pH, buffer, and temperature on the molar absorptivity are also reported.
Absorption↗
[The NBT test. II. Uses].
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Collagen Diseases↗
[Inhibition of electron transport and photophosphorylation in chloroplasts by quercetin].
The influence of quercetin on electron transport and photophosphorylation of pea isolated chloroplasts with methylviologen and NADP+ has been studied. Quercetin inhibits ATP synthesis and phosphorylating electron transport but does not affect the basal electron transport in the presence of methylviologen. In view of these data and because of the increase of the proton uptake by chloroplasts in the presence of quercetin we consider it as an inhibitor of energy transfer. Under conditions of NADP+ photoreduction quercetin acts also as an inhibitor of electron transfer, interacting with ferredoxin, though a complete inhibition of electron transfer has not been observed. This last phenomenon may be of importance for the understanding of the detailed mechanism of NADP+ reduction by chloroplasts.
Chloroplasts↗
Enzymatic determination of blood ethanol, with amperometric measurement of rate of oxygen depletion.
A rapid electrochemical measurement of blood ethanol is proposed. Alcohol is oxidized by NAD+ in the presence of alcohol dehydrogenase; and the NADH produced is aerobically oxidized by horseradish peroxidase. The rate of depletion of buffer-carried oxygen, which is directly proportional to the alcohol concentration in the sample, is amperometrically monitored with a membrane oxygen-sensing electrode. Only a 5-microliter sample of whole blood is required, with no deproteinization, incubation, extraction, or dilution. Results, obtained in less than 1 min, correlate well with those obtained by gas-chromatographic and spectrophotometric methods.
Alcohol Oxidoreductases↗
Glucose oxidation in the chick cornea: effect of diamide on the pentose shunt.
Chick embryo corneas (stages 38 and 45) have been used to study variations in pentose shunt activity following the use of a glutathione-specific oxidizing agent, diamide, and a sulfydryl blocking agent, N-ethylmaleimide (NEM). Shunt activity was measured by the ratio of radiolabeled carbon 1 (14C-1) of glucose to radiolabeled carbon 6 (14C-6) of glucose derived as expired 14CO2. Diamide and NEM were both found to increase pentose shunt activity relative to glycolysis, although by different means. Diamide appeared to exert its effect by oxidizing glutathione and creating a demand for higher shunt activity to facilitate glutathione reduction by NADPH. Both C-1 and C-6 oxidation were increased, but C-1 oxidation was increased to a much greater extent. In contrast, NEM decreased both C-1 and C-6 oxidation, with C-6 preferentially affected. Thus NEM appears to preferentially inhibit the enzymatic machinery of the glycolytic-tricarboxylic acid cycle pathway and acts as an effective metabolic stress on the cornea. Our data suggest that the pentose shunt in the cornea may serve as an important alternative pathway under conditions of metabolic stress for glucose utilization and the production of energy (ATP) in the corneal cells.
Animals↗
Oxidative-reductive modulation of guinea pig splenic cell guanylate cyclase activity.
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Animals↗
Copper catalyzed alkaline autoxidation of selenocystamine.
In alkaline medium and in the presence of cupric ions selenocystamine undergoes autoxidation and is entirely transformed into selenohypotaurine. Among the different metal ions tested, Fe, Co, Ni, Cu, Ag, Mg, Mn, only cupric ions are effective in catalyzing the reaction. The reaction shows an optimum around pH 13. In most respects the autoxidation of selenocystamine is similar to the alkaline autoxidation of cystamine. Some data on the paper and ion exchange chromatographic behaviour of selenohypotaurine and selenotaurine are reported, as also details for the synthesis of selenotaurine.
Cations, Divalent↗
Autooxidation and hydroxylation reactions of oxygenated cytochrome P-450cam.
Oxy-ferrous substrate-bound cytochrome P-450cam (mrsO2) autooxidizes in the absence of its specific effector protein, putidaredoxin, without hydroxylating the substrate, camphor. The autooxidation is first order with an activation energy of 17 kcal mol-1 at 25 degrees, pH 7.0. Substrate removal and low pH accelerate the reaction. The product, 5-exo-OH camphor, and a nonhydroxylated pseudosubstrate, norcamphor, stabilize the complex in a manner similar to camphor. Increased oxidation rate of mrsO2 and substrate hydroxylation are induced by putidaredoxin, rebredoxin, cytochrome b5, and the apoproteins of the latter two. Dihydrolipoic acid and other dithiols also replace putidaredoxin as effector molecules, but 1000-fold higher concentrations are required. Effector molecules do not increase the autooxidation rate of mrsO2 unless camphor, norcamphor, or another pseudosubstrate is present. Kinetic evidence is presented showing that an active complex between mrsO2 and effector is a required intermediate in mixed function oxidation.
Animals↗
Crosslinking of the nearest membrane protein neighbors in ATP depleted, calcium enriched and irreversibly sickled red cells.
ATP depleted or Ca2+ (0.1 mM) enriched normal red cells (greater than 80% echinocytes III) subjected to crosslinking by catalytic oxidation contain a greater than 1,000,000 daltons spectrin rich polymer cleavable by dithiothreitol (DTT) reduction. Similar complex is seen after glutaraldehyde crosslinking suggesting spectrin rearrangement into closer contacts or aggregation. In addition, a non-reducible greater than 1,000,000 daltons polymer is produced in fresh rbc or ghosts by high (greater than 0.5 mM) Ca2+ conc. and ionophore A23187. This complex is attributed to endogenous membrane protein crosslinking, catalyzed by a Ca2+ stimulated rbc transglutamidase. ISCs exhibiting a 4 fold increase in Ca2+ and a decrease in ATP do not exhibit these polymers. However, ISCs have an increased propensity to form the spectrin rich polymer during a subsequent ATP depletion and this is associated with a transformation of greater than 60% ISCs into spheroechinocytes. Similar cells are occasionally noted (greater than 4%) in the densest ISC rich fractions separated from fresh blood. We conclude that neither Ca2+, ATP dependent spectrin aggregation nor a spontaneous irreversible crosslinking underlie the membrane lesion of ISCs. Accelerated calcium gain and ATP depletion in ISCs leads to spectrin rearrangement and transformation of ISCs into spheroechinocytes which may represent an end stage ISC lesion resulting in an ISC removal from circulation.
Adenosine Triphosphate↗
[Light activation of NADH and NADPH].
Illumination of NADH and NADPH by UV-light in the absence of oxygen resulted in the reduction of ferredoxin or methyl-viologen to cation-radical and under prolonged illumination to dihydrodipyridyl. The reaction may by accompanied by triplet and singlet exitation of NADH. It was shown that hematoporphyrin in aqueous solution photosensitized the reaction of NADH oxidation by ferredoxin and methylviologen to the visible region of the spectrum. Under light excitation the redox potentials of NADH and NADPH were increased up to the level exceeding the potential of hydrogen electrode. Illumination of NADH and NADPH by UV-light in the presence of bacterial hydrogenase resulted in hydrogen evolution. The reaction of hydrogen evolution could be sensitised towards the visible region of the spectrum by chlorophyll or chloroplasts.
Catalysis↗
[Effect of N-alkylimidazoles on oxidation of o-dianizidine catalyzed by horseradish peroxidase].
Effect of a number of N-alkylimidazoles (from N-methyl to N-octylimidazole) on peroxidase oxidation of o-dianizidine at pH 8.0 is studied. Alkylimidazoles studied are found to activate the reaction under given conditions, the activation type being non-competitive KA and (alpha) values are similar for all the activators, which suggests a similar mechanism of their action. Similar KA values suppose an insignificant role of hydrophobic interactions in the binding of N-alkylimidazoles with the enzyme.
Benzidines↗
Studies on metabolism of bromazepam. VI. Reduction of 2-(2-amino-5-bromobenzoyl)pyridine, a metabolite of bromazepam, in the rabbit, rat, and guinea pig.
Three urinary metabolites that were formed by cleavage of the benzodiazepine ring of bromazepam, 2-(2-amino-5-bromobenzoyl)pyridine (ABBP), 2-(2-amino-5-bromo-3-hydroxybenzoyl)pyridine (3-OH-ABBP), and 2-amino-5-bromo-2'-azabenzhydrol (ABAB), were measured in urine of rabbits, rats, and guinea pigs. The major metabolite was 3-OH-ABBP in all animals given bromazepam orally. ABAB was also excreted in major amounts in the guinea pig, but was excreted in minor amounts in the rabbit and rat. Moreover, ABAB was excreted in the urine of all animals given ABBP orally. It may be concluded that ABAB was formed by reduction of the carbonyl group of ABBP. ABBP reduction was catalyzed by NADPH-dependent enzymes occurring in rabbit liver cytoplasm, and rat liver microsomes, and guinea pig liver cytoplasm and microsomes. The reductases were inhibited by sulfhydryl group reagents. The optimum pH of the cytoplasmic enzyme ranged from 7.2 to 7.8, and that of the microsomal enzyme was 6.5. The apparent KM value for the reduction of ABBP by guinea pig liver microsomes was the lowest among all of the liver preparations.
Animals↗
Microsomal mixed-function amine oxidase. Oxidation products of piperazine-substituted phenothiazine drugs.
Oxidation products of fluphenazide, thioproperazine, and trifluoperazine obtained in reactions catalyzed by homogeneous preparations of the microsomal mixed-function amine oxidase have been isolated and identified. Approximately 0.5 g of metabolite of each piperazine-substituted phenothiazine drug was prepared in reactors containing, as catalyst, the purified oxidase covalently attached to glass beads. Nuclear magnetic resonance spectra of the isolated products indicated that with all three substrates the enzyme preferentially catalyzes N-oxidation of the piperazine nitrogen furthest from the phenothiazine nitrogen atom. The enzyme-catalyzed oxidation is quite specific and oxidation of the sulfur or nitrogen atoms in the phenothiazine ring could not be detected. Concentrations of piperazine-substituted phenothiazines required to half-saturate the amine oxidase were in the micromolar range and at pH 8.3 and 37 degrees C, all those tested were oxidized at approximately 2 mumol/min/mg of enzyme. Kinetic constants for the piperazine-substituted phenothiazines were very similar to those obtained with phenothiazines containing a dimethylaminopropyl sidechain.
Animals↗
Elimination of radioactivity following administration of [15,16-3H]naltrexone to rats and guinea pigs.
The elimination of radioactivity after [15,16-3H]naltrexone administration was studied in rats and guinea pigs. An average of 42% of the dose was eliminated in urine and 55% in feces following administration of 1 mg/kg iv to each of three rats. Analysis of radioactivity in the excreta of one rat that received the same dose im yielded similar results. On the other hand, four guinea pigs that received 1 mg/kg iv excreted only 14% of the dose in feces and 84% in urine. Similar results were obtained following im administration to guinea pigs at 1 and 20 mg/kg doses. In guinea pig excreta, an average of 64% of the dose corresponded to naltrexone and conjugates, 19% to beta-naltrexol and conjugates, and 2% to alpha-naltrexol and conjugates. In urine, the radioactivity corresponding to alpha-naltrexol and naltrexone was present mainly in conjugated form, whereas apparent beta-naltrexol was mainly unconjugated. The radioactivity in feces corresponded principally to unconjugated naltrexone and beta-naltrexol.
Animals↗
Proteins containing reductively aminated disaccharides: chemical and immunochemical characterization.
Synthetic glycoproteins can be prepared by reductive amination of proteins and reducing carbohydrates in the presence of sodium cyanoborohydride. The reaction proceeds readily in aqueous solution at pH 6--9 to give high degrees of substitution. The degree of substitution can be determined by amino acid analysis, as the 2 degrees amine linkage formed with the epsilon-amino groups of lysine is stable to acid-catalyzed protein hydrolysis conditions. Antisera have been obtained to bovine serum albumin conjugates containing reductively aminated cellobiose, lactose, and maltose. Preliminary experiments demonstrate that antiserum to the cellobiose-BSA conjugate is hapten-specific, and the structural features of the hapten recognized by the antibodies were established by hapten inhibition experiments. These studies demonstrate that antibodies recognize both the terminal beta-glucosyl and acyclic reduced glucosyl residues.
Amination↗