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PubMed1975

[Ferrous ion oxidation and uranium solubilization from a lowgrade ore by "Thiobacillus ferrooxidans" (author's transl)].

The microbiological oxidation of ferrous ion and the extraction of uranium from a low-grade ore has been studied using an adapted strain of Thiobacillus ferrooxidans. The effect of temperature, pH, volumetric oxygen transfer coefficient, K1a, and aeration number, Ia, on the activity of the microorganism has been determined. The activation energy for ferrous iron oxidation was calculated to be - 13.9 +/- 0.1 kcal/mole and inactivation (thermal death of bacteria) 53.3 +/- 0.2 kcal/mole. Temperature coefficient, Q10, was estimated to be 1.8. Uranium extraction varied between 80 and 100%.

Hydrogen-Ion Concentration↗
PubMed1976

Hydrogen exchange at the amide group of reduced pyridine nucleotides and the inhibition of that reaction by dehydrogenases.

Stopped flow ultraviolet spectroscopy has been used to measure the rate of hydrogen exchange with solvent at the amide group of reduced nicotinamide nucleotide coenzymes. Several mechanisms for the exchange reaction are considered in the light of the kinetic data. Complex formation between the coenzyme and any of four dehydrogenases markedly slows the rate of hydrogen exchange. Hydrogen bond formation and/or hydrophobic interactions within these complexes are thought to be the reasons for the decreased rate of exchange.

Alcohol Oxidoreductases↗
PubMed1976

The metabolic activation of the carcinogen 1'-hydroxysafrole in vivo and in vitro and the electrophilic reactivities of possible ultimate carcinogens.

Administration of [2',3'-3H]-1'-hydroxysafrole to rats or mice resulted in the formation of hepatic DNA-, ribosomal RNA-, and protein-bound 3H derivatives. Alkaline digestion of the 3H-protein released 0.1 to 0.3% of the 3H as a derivative that was identified as 3'-methylmercaptoisosafrole by its cochromatography in five solvent systems with the synthetic compound. 1'-Hydroxysafrole was metabolized at a low rate by rat and mouse liver cytosols in a 3'-phosphoadenosine 5'-phosphosulfate-dependent reaction to a derivative (presumably the sulfuric acid ester) that was captured by its reaction with RNA. Likewise, 1'-hydroxysafrole was oxidized at a low rate by rat and mouse liver microsomes to 1'-hydroxysafrole-2',3'-oxide in a reduced nicotinamide adenine dinucleotide phosphate-dependent reaction. Both of these electrophilic metabolites are candidate ultimate carcinogenic derivatives of 1'-hydroxysafrole. The electrophilic reactivities of various safrole derivatives with nucleosides were determined to be in the order of 1'-oxosafrole greater than 1'-acetoxysafrole greater than 1'-acetoxysafrole-2',3'-oxide greater than 1'-hydroxysafrole-2',3'-oxide greater than safrole-2',3'-oxide greater than or equal to 1'-oxosafrole-2',3'-oxide. The major reactions were generally observed with guanosine. A major reaction product of 1'-acetoxysafrole and guanosine 5'-monophosphate yielded 3'-hydroxyisosafrole under very mild acidic conditions. These data further substantiate the previous characterization of this reaction product as O-6-(isosafrol-3'-yl)guanylic acid. The syntheses of 1'-oxosafrole, 2',3'-dehydrosafrole, [2',3'-3H]-1'-hydroxysafrole, and the 2',3'-oxed.

Acetyltransferases↗
PubMed1976

[Disadvantages of acid precipitation of proteins during the assay of blood glucose by the enzymatic glucose oxidase-peroxidase system].

In the enzymatic procedure for blood sugar by means of glucose oxidase, acid protein precipitation of blood by perchloric acid or trichloracetic acid liberated oxidizing substances, which enhanced the coloration density in oxidizing the reduced chromogen of the reaction mixture, independently of the hydrogen peroxide generated from glucose, and would give false high values of glycemia, if additional precautions had not been taken. These substances, increasing considerably with times and temperature of blood conservation, would be of peroxide nature, and would accumulate in red blood cells during their exposure to air.

Animals↗
PubMed1975

Luminescence and respiratory activities of Photobacterium phosphoreum. Competition for cellular reducing power.

Changes in the in vivo luminescence, respiratory activities, contents of cytochromes, extractable luciferase and NAD(P)H-FMN reductase during growth of the wild (bright) strain of Photobacterium phosphoreum and its dim mutant were determined. The intensity of the in vivo luminescence per cell increased 10 times in the wild strain and 750 times in the dim strain during logarithmic growth, while the contents of luciferase and NAD(P)H-FMN reductase remained almost constant. It is suggested that a characteristic change in the mode of competition of the luminescence reaction system with another electron transfer chain involving cytochromes for NAD(P)H take place during the growth of this bacterium.

Cell Division↗
PubMed1976

Pulse radiolytic investigation of single heme group reduction in hum an methemoglobin.

Reduction of one of the four heme groups of human aquomethemoglobin A has been investigated by the pulse radiolysis method. The reactivity of e-a-q, the hydrated electron, with methemoglobin was determined by observing this species directly. The separate reactions of the hydroxy yl radical and hydrogen atom, as well as of e-a-q, were studied by observing absorbance changes in the protein spectrum over the wavelength range 290 to 600nm, with appropriate scavengers in solution...

Azides↗
PubMed1975

Early changes in myocardial hypoxia: relations among mechanical function, pH, and intracellular redox states.

When rat hearts were subjected to abrupt hypoxia the onset of NADH changes as measured by epicardial fluorescence and of depressed contractility occurred at similar times. Direct measurements of changes in tissue metabolism lagged behind changes in fluorescence and contractility. Calculated NAD:NADH ratios became reduced more rapidly and to a greater extent in the cytoplasm than in the mitochondria, but did not necessarily signal greater changes in total NADH. The detection of depressed contractility before a fall in intracellular pH or a rise in intracellular lactate casts doubt on the postulate that an increase in hydrogen ion is the primary cause of hypoxic myocardial failure.

Animals↗
PubMedDate not supplied

Oxisuran reduction by rabbit tissue preparations.

Oxisuran, 2-((methylsulfinyl)acetyl)pyridine is reduced to alpha-((methylsulfinyl)methyl-2-pyridinemethanol, oxisuranol, by cytoplasmic enzymes from rabbit liver, kidney, brain, intestine, and lung. The cytoplasmic enzyme from liver is dependent on NADPH as cofactor and has an optimal pH of 6.0. Enzymatic activity is also present in liver mitochondria but at a lower specific activity. The cytoplasmic extracts catalyze the formation of two oxisuranol products, presumably the diastereoisomers described by Di Carlo and associates from in vivo studies. Verification of the product as oxisuranol was accomplished by thin-layer chromatography and mass spectrometry.

Animals↗
PubMed1976

Mechanism of the irreversible inhibition of aspartate aminotransferase by the bacterial toxin L-2-amino-4-methoxy-trans-3-butenoic acid.

The naturally occurring toxin L-2-amino-4-methoxy-trans-3-butenoic (AMB) acid irreversibly inhibits pyridoxal phosphate-linked aspartate aminotransferase. The inhibitor is a substrate for the enzyme, and as such is converted into a highly reactive intermediate which chemically reacts with an active site residue, thus irreversibly inactivating the enzyme. Enzymological and model studies on AMB are presented which enable one to determine the precise mechanism of action of this toxin. The mechanism involves Schiff base formation between the enzyme and toxin followed by alpha-C--H bond cleavage and aldimine isomerization to generate a bifunctional Michael acceptor. This molecule alkylates an active site residue by an addition and elimination route.

Aminobutyrates↗
PubMed1976

Differential reactivity of the two active site cysteine residues generated on reduction of pig heart lipoamide dehydrogenase.

Reduction of the active center disulfide bond in the flavoprotein pig heart lipoamide dehydrogenase generates two sulfur moieties which are chemically inequivalent in the 2-electron reduced form of the enzyme. Thus 1 cysteine residue is at least 13-fold more reactive than its partner toward iodoacetamide at pH 7.6. This selectivity was demonstrated by reaction of the 2-electron reduced enzyme with a low concentration of iodo[1-14C]acetamide under anaerobic conditions. The formation of a monolabeled derivative is accompanied by the reappearance of a spectrum of oxidized bound flavin, clearly different from that of the native enzyme. Alkylation of the remaining cysteine residues with iodo[12C]acetamide enabled the isolation of a tryptic version of the active center disulfide peptide. A single chymotryptic cleavage between the 2 alkylated cysteine residues generated a cationic and an anionic fragment containing 7% and 93% of the radioactivity of the purified tryptic peptide, respectively. The monolabeled derivative is catalytically inactive toward reduced or oxidized lipoamide, but is approximately 2-fold better as a transhydrogenase than the native protein using NADH and acetylpyridine adenine dinucleotide as substrates. Anaerobic titration with NADH leads to reduction of the flavin with concomitant formation of long wavelength absorption of low intensity. No intermediate reduced states were detected in this titration analogous to the red 2-electron form observed with the native enzyme. Similarly, intermediates during reduction of the enzyme by 1 eq of dithionite have not been detected.

Anaerobiosis↗
PubMed1976

Dissociation of CO from carboxyhemoglobin.

The reaction between carboxyhemoglobin and reduced microperoxidase (MP): Hb4(CO)4 + 4MP=Hb4 + 4MPCO, recently reported by us, has been further studied. By generating species Hb4(CO), Hb4(CO)2, and Hb(CO)3 in the stopped flow cuvette by the reaction of dithionite with the species of the general formula Hb4(O2)x(CO)y(x + y=4) in the presence of microperoxidase it has been possible to determine the stepwise CO dissociation rate constants l4, l3, l2, and l1. The overall CO dissociation rate constant l, which is the same in this system as l4, is not affected by 2,3-diphosphoglyceric acid. The activation energy of the reaction is 21,400 cal in 15-25 degrees range. The ratio deltal/deltapH is approximately 3 in 6.5 to 7.5 pH range. The kinetic data indicate that, compared to HbO2, the contribution to the cooperativity of the dissociation rate constants of carboxyhemoglobin is greatly reduced. The ligand-dependent differences in the reactions of Hb with CO, O2, and NO suggest that in the combination reactions the ligand plays an active role in the rate-limiting step.

Carbon Monoxide↗