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PubMedDate not supplied

Biotransformation of prochiral 2-phenyl-1,3-di(4-pyridyl)-2-propanol to a chiral N-oxide metabolite.

The prochiral compound, 2-phenyl-1,3-di(4-pyridyl)-2-propanol (PPP) labeled with 3H in the phenyl ring, was administered to rats, dogs, and a human subject. Paper chromatography of the urine indicated that a major metabolite common to all three species was excreted. This metabolite was isolated from the urine of chronically dosed dogs and was identified by mass, nuclear magnetic resonance (NMR), and infrared spectrometry as the N-oxide, 2-phenyl-1-(4-pyridyl)-3-(4-pyridyl-1-oxide)-2-propanol. In addition, polarimetry indicated that this metabolite was levorotatory. Examination of the enantiomeric purity of a crystallized sample of the metabolite by NMR spectroscopy of resolvable diastereomeric salts formed with lasalocid revealed the presence of only the levorotatory enantiomer. Accordingly, this metabolic N-oxide formation in the dog was at least stereoselective, and perhaps stereospecific. The N-oxidation of PPP was also demonstrated in vitro with 9000 g supernatant fraction of rat liver fortified with an NADPH generating system, and this reaction was inducible by phenobarbital, indicating that it is mediated by the cytochrome P-450 mixed-function oxidase system. This study, in addition to providing another example of the pyridyl N-oxidation pathway, illustrates the necessity of considering the stereochemical aspects of the metabolism of prochiral drugs.

1-Propanol↗
PubMedDate not supplied

On the product of the reaction between cysteamine and 3-bromopyruvate.

Some properties of TZCA, the addition compounds of cysteamine and 3-bromopyruvate, have been investigated. From the behaviour of the UV absorption spectra in acidic and alkaline solutions in the presence or absence of oxygen, it was shown that the instability of TZCA was imputable to an oxidative degradation. It was further shown that TZCA undergoes in alkali spontaneous oxidative decarboxylation, and that the arising product may be hydrolyzed to cystamine and glyoxylic acid. Some chemical reactions and the paper chromatographic behaviour of TZCA are reported. It was shown that TZCA, despite its great instability, may be the reactions described, and thus differentiated from other adducts of bromopyruvate and different aminothiols.

Chemical Phenomena↗
PubMed1979

Mixed function oxidases in sterol metabolism. Separate routes for electron transfer from NADH and NADPH.

Oxidative deformylation of 4-hydroxy[14C]methylene-5alpha-cholest-7-en-3-one and oxidative demethylation of [30,31-14C]4,4-dimethyl-5alpha-cholest-7-en-3beta-ol by rat liver microsomes have been compared with regard to the manner in which electrons are introduced from both NADH and NADPH. Evidence suggests that NADH and NADPH support oxidation of both substrates via separate routes of electron transfer. Thus, 10 micron cytochrome c will inhibit NADPH-supported oxidation to 40 to 50% of control activity leaving NADH-supported oxidation unaffected. Also, treatment of microsomes with subtilisin diminishes NADPH-supported oxidation to 10 to 30% of control activity for either substrate to 70 to 90% of control activity while NADH-supported oxidative activity is virtually unaffected. Studies on the oxidase activities and NADPH-cytochrome c reductase as well as NADH-ferricyanide reductase have shown marked differences in activity in the presence of inhibitors. Thus, 9 mM 2'-AMP inhibits NADPH-cytochrome c reductase to 10 to 20% of control activity while NADPH-supported oxidative demethyl ation and deformylation are essentially unchanged. Mersalyl at 15 to 25 nmol/mg of microsomal protein inhibits both reductases to 20 to 40% of control activity; oxidative demethylation is unaffected and oxidative deformylation stimulated slightly when NADPH is used. Finally, antibody to NADPH-cytochrome c reductase inhibits oxidase activity for either substrate to 70 to 90% of control activity while reductase activity is inhibited to 10 to 30% of control activity.

Animals↗
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↗