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At least 631 records · Page 35Linked to original sources
PubMed1978

[Kinetics and mechanism of nucleophilic effect on the oxidation of o-dianisidine catalyzed by horseradish peroxidase].

The effects of benzimidazole and 4-nitroimidazole on the reaction of o-dianisidine peroxidase oxidation within the pH range of 3.7--9.0 were studied. Both substituted imidazoles activate the reaction at less than 0.6. In the presence of 4-nitroimidazole the activation is non-competitive, whereas in the presence of benzimidazole it is of a mixed type, which is close to the non-competitive one. The kinetic parameters (kAcat, alpha, KA) for the reaction activated by both imidazoles were determined. It was assumed that the activators interact with the protein group (pK approximately to 6.5), which limits the enzyme activity. This results in the increase of pKapp of the protein group in question, resulting in the appearance of the maximal peroxidase activity in the alkaline region of pH. It was shown that the intermolecular interactions involved in the peroxidase-induced oxidative catalysis are largely due to electrostatic rather than to hydrophobic factors.

Benzidines↗
PubMedDate not supplied

[Photoinduced reduction of NAD(P) in the cells of green sulfur bacteria].

The spectrum of a photoinduced increase in luminescence of the cells of the gree sulphur bacterium Chlorobium limicola f. thiosulfatophilum, within the range of 400 to 520 nm, was found to correspond to the spectrum of luminescence of NADH in the protein-bound form. Photoinduced reduction of NAD(P) in green bacteria, contrary to purple bacteria, is not susceptible to the action of p-chlorocarbonylcyanide phenlhydrazone which uncouples photophosphorylation. Therefore, in Chlorobium limicola f. thiosulfatophilum, NAD(P) is reduced by direct non-cyclic transport of electrons via the photosynthetic chain. NAD(P)H is utilized mainly in the system of CO2 fixation; the process is inhibited by fluoroacetate, and the inhibition is eliminated by substrates of the cycle of carboxylic acids.

Carbon Dioxide↗
PubMedDate not supplied

[Changes in oxidative systems of liver microsomes in rats following a single administration of phenobarbital and morphine].

During the first three hours after a single administration of phenobarbital or morphine into rats a marked increase was observed in the activity and content of the respiratory chain components responsible for the oxidation of NAD-H2 and NADP-H2 in liver microsomes. This activation of oxidative enzymes correlated with the disappearance of hypnotic and analgetic effects of the narcotics. The phase following the normalization of oxydative systems was characterized by the increase of microsomal enzymes level. This is related to their specific induction only by phenobarbital.

Animals↗
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↗