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PubMed1991

The FAD-containing monooxygenase-catalyzed N-oxidation and demethylation of trimethylamine in rat liver microsomes.

Trimethylaminuria (TMAuria), the excessive urinary excretion of the odorous trimethylamine (TMA), accompanies elimination of TMA in sweat and corresponding "fish-odor" syndrome. TMA was oxidized in vitro in rat liver microsomes from male Sprague-Dawley rats to TMA N-oxide and N-demethylated to dimethylamine (DMA). Both reactions were inhibited to 1-3% of normal activity by preincubation of microsomes without NADPH-generating system at 37 degrees C for 10 minutes indicating the FAD-containing monooxygenase-catalyzed reactions. On the other hand, the reactions were not inhibited by gas phase containing up to 80% carbon monoxide/20% oxygen mixture. The results are compatible with the hypothesis that in rat liver microsomes the N-oxygenation and N-demethylation of TMA are catalyzed only or predominantly by FAD-containing monooxygenases, and the cytochrome P-450 monooxygenases play a negligible, if any, role.

Animals↗
PubMed1996

Mitochondrial FAD-glycerophosphate dehydrogenase and G-protein-coupled inwardly rectifying K+ channel: No evidence for linkage in maturity-onset diabetes of the young or NIDDM.

Two genes that have potentially important regulatory roles in insulin secretion are both located on chromosome 2q24.1. G-protein-coupled muscarinic potassium channel (GIRK1) is an inwardly rectifying K+ channel that helps to maintain the resting potential and excitability of cells. Mitochondrial FAD-linked glycerophosphate dehydrogenase (m-GDH) catalyzes a rate-limiting step of the glycerol phosphate shuttle in pancreatic islets. Reduced m-GDH activity has been demonstrated in islets isolated from diabetic subjects compared with islets from nondiabetic control subjects and from the diabetic GK rat. To study the relationship between these candidate genes and NIDDM, we have examined a simple tandem-repeat polymorphism (STRP) close to both the KCN J3 (GIRK1) locus and the m-GDH locus. In a linkage study of three maturity-onset diabetes of the young (MODY) pedigrees, not linked to MODY1, MODY2, or MODY3, a cumulative score of - 9.6 at a recombination fraction of theta = 0 excluded linkage. In a population-association study, no linkage disequilibrium for the STRP was found between 190 unselected NIDDM patients and 60 geographically and age-matched white nondiabetic subjects (chi2 = 1.51 on 3 df, P = 0.68). Thus, mutations involving the genes for GIRK1 or FAD-glycerophosphate dehydrogenase are unlikely to cause MODY, and a common mutation in either gene is unlikely to contribute to NIDDM in whites. These data do not exclude mutations in some families or other ethnic groups.

Animals↗
PubMed1984

The measurement of FAD-containing mono-oxygenase activity in microsomes containing cytochrome P-450.

Antibodies to NADPH-cytochrome P-450 reductase have been used to essentially abolish the contribution of cytochrome P-450 to xenobiotic metabolism by mammalian microsomes. This permits the determination of the activity of the FAD-containing mono-oxygenase and the stoichiometry between substrate, O2 and NADPH, in the microsomal membrane, and in the absence of cytochrome P-450-dependent activity. FAD-containing mono-oxygenase oxidation rates were determined for sulphur- and nitrogen-containing substrates, including: thiols; sulphides; thioamides; primary, secondary and tertiary amines; hydrazines. Although the enzyme in mouse, rabbit, rat and pig microsomes displays similar substrate specificity, some catalytic characteristics are different between species and tissues.

Animals↗
PubMed1992

Involvement of FAD-dependent polyamine oxidase in the metabolism of milacemide in the rat.

1. It has previously been established that monoamine oxidase (MAO)-B participates in the metabolism of milacemide [2-(pentylamino)acetamide]. Furthermore, in rats, inhibition of FAD-dependent polyamine oxidase (PAO) was found to decrease the urinary excretion of two milacemide metabolites, termed UK1 and UK2. 2. Using gas chromatography-mass spectrometry, UK1 was identified as oxamic acid and UK2 as 2-hydroxyacetamide, confirming that PAO is involved in the metabolism of milacemide. 3. Thus, two FAD-dependent amine-oxidizing enzymes, MAO and PAO, contribute to the metabolism of milacemide. Milacemide appears to be the first non-polyamine xenobiotic in the metabolism of which PAO participates.

Acetamides↗
PubMedDate not supplied

[The activity of glutathione-reductase and FAD-effect as indicators of the riboflavin level in experiments and in patients with phenylketonuria].

Subjects of discussion in the paper are various methods of determining the riboflavin allowances and the results achieved by the application of two of them that concern determining the activity of the glutathione-reductase and the FAD-effect in the study of an experimental B2-deficiency in rats and the riboflavin allowances in children suffering from phenylketonuria. Exclusion of vitamin B2 from the ration of rats resulted in that in 8 weeks they developed B2-deficiency ascertained with the help of the above cited enzymatic tests. In a certain percentage of children with phenylketonuria after discontinued administration of group "B" vitamins (D1 diet) there could be observed an intensification of the FAD-effect and, accordingly, a reduced glutathione-reductase activity. Resumed taking of the vitamins (D2 diet) normalized the riboflavin allowance values in at least, one week's time.

Animals↗
PubMed2002

Spotting management fads.

Business fads can change companies, for better or worse. They can introduce useful ideas but often fail to deliver on promises. So how can managers tell a fad from a tool that might endure? For one thing, beware of suspiciously simple techniques. If they seem too easy, they probably are.

Administrative Personnel↗
PubMed1992

FAD-dependent regulation of transcription, translation, post-translational processing, and post-processing stability of various mitochondrial acyl-CoA dehydrogenases and of electron transfer flavoprotein and the site of holoenzyme formation.

The most prominent biochemical consequence of riboflavin deficiency in rats is a drastic decrease in various acyl-CoA dehydrogenase activities, especially that of short chain and isovaleryl-CoA dehydrogenase (IVD). As a result, oxidation of fatty acids and leucine is severely inhibited. We studied the effects of FAD at various stages of acyl-CoA dehydrogenase biogenesis. Immunoblot revealed severe losses of various acyl-CoA dehydrogenases and electron transfer flavoprotein in riboflavin-deficient rat liver mitochondria. The decreases in IVD and short chain acyl-CoA dehydrogenase were particularly severe, reaching values of 17 and 34% of controls, respectively. With the exception of IVD, the rate of in vitro transcription of the respective genes and the amounts of mRNAs of these flavoproteins in tissues increased 3-8.5-fold over controls. The amount of IVD mRNA and its transcription rate remained unchanged, suggesting that IVD expression is regulated separately from other acyl-CoA dehydrogenases. When riboflavin was depleted, in vitro translation of acyl-CoA dehydrogenase and electron transfer flavoprotein alpha-subunit mRNAs was moderately inhibited. Translation of non-flavoproteins was also inhibited. The stability of precursor acyl-CoA dehydrogenases and their mitochondrial import/processing were unaffected. However, mature acyl-CoA dehydrogenases degraded markedly faster in deficient mitochondria than in controls. Regardless of whether precursors were translated under riboflavin-depleted or riboflavin replete conditions, mature acyl-CoA dehydrogenases survived well when imported into normal mitochondria but degraded faster when imported into deficient mitochondria. These findings indicate that FAD ligand binds to mature acyl-CoA dehydrogenase inside the mitochondria.

Acyl-CoA Dehydrogenases↗
PubMed1992

Roles of FAD and 8-hydroxy-5-deazaflavin chromophores in photoreactivation by Anacystis nidulans DNA photolyase.

DNA photolyase from the cyanobacterium Anacystis nidulans contains two chromophores, flavin adenine dinucleotide (FADH2) and 8-hydroxy-5-deazaflavin (8-HDF) (Eker, A. P. M., Kooiman, P., Hessels, J. K. C., and Yasui, A. (1990) J. Biol. Chem. 265, 8009-8015). While evidence exists that the flavin chromophore (in FADH2 form) can catalyze photorepair directly and that the 8-HDF chromophore is the major photosensitizer in photoreactivation it was not known whether 8-HDF splits pyrimidine dimer directly or indirectly through energy transfer to FADH2 at the catalytic center. We constructed a plasmid which over-produces the A. nidulans photolyase in Escherichia coli and purified the enzyme from this organism. Apoenzyme was prepared and enzyme containing stoichiometric amounts of either or both chromophores was reconstituted. The substrate binding and catalytic activities of the apoenzyme (apoE), E-FADH2, E-8-HDF, E-FAD(ox)-8-HDF, and E-FADH2-8-HDF were investigated. We found that FAD is required for substrate binding and catalysis and that 8-HDF is not essential for binding DNA, and participates in catalysis only through energy transfer to FADH2. The quantum yields of energy transfer from 8-HDF to FADH2 and of electron transfer from FADH2 to thymine dimer are near unity.

Apoenzymes↗
PubMed1990

Xanthine oxidase-catalyzed reductive debromination of 6-(bromomethyl)-9H-purine with concomitant covalent modification of the FAD prosthetic group.

Bovine milk xanthine oxidase was potently inhibited by 6-(bromomethyl)-9H-purine in a time-dependent process with O2 as the electron acceptor. If the enzyme were assayed with phenazene ethosulfate as an electron acceptor, 6-(bromomethyl)-9H-purine was not an inhibitor. The rate of formation of inhibited enzyme increased with increasing concentrations of 6-(halomethyl)-9H-purine, decreased with increasing concentrations of O2, and increased in the presence of xanthine. The inhibited enzyme regained activity nonactinically at pH 7 with a t1/2 of 31 h. The optical difference spectrum between native enzyme and inhibited enzyme suggested that the enzyme-bound FAD was modified. This conclusion was confirmed by demonstrating that activity was restored to the inhibited enzyme if the enzyme-bound flavin was removed by treatment with CaCl2 and the resulting apoenzyme was reconstituted with FAD. Aerobically, 6-(bromomethyl)-9H-purine was oxidized by the enzyme to a species having a UV spectrum consistent with hydroxylation of the purine ring to form a urate analogue. Anaerobically, the enzyme reduced 6-(bromomethyl)-9H-purine to 6-methylpurine with 1 mol of enzyme being completely inhibited after reduction of 23 mol of 6-(bromomethyl)-9H-purine. Thus, 6-(bromomethyl)-9H-purine was not only oxidized by xanthine oxidase but was also reduced by the enzyme in a reaction that partitioned between formation of 6-methylpurine and inhibition of the enzyme by modification of the enzyme-bound flavin. Similar results were found when 6-(chloromethyl)-9H-purine was the inhibitor.

Animals↗
PubMed1977

Nitrate reductase from Spinacea oleracea. FAD and the reactivation of the enzyme treated with p-Hydroxymercuribenzoate.

Spinach nitrate reductase complex previously inactivated by treatment with mercurials p-hydroxymercuribenzoate or p-hydroxymercuriphenyl sulphonate can be reactivated by incubation with dithioerythritol. The reactivation of NADH-diaphorase seems to be FAD-dependent, whereas that of FNH2-nitrate reductase is not. The requirement of FAD for NADH-inactivation of nitrate reductase treated with p-hydroxymercuribenzoate disappears after treatment with dithioerythritol.

Dihydrolipoamide Dehydrogenase↗
PubMed1981

The reductive half-reaction of liver microsomal FAD-containing monooxygenase.

The addition of substrates to microsomal FAD-containing-monooxygenase (EC 1.14.13.8) is an ordered process in which FAD reduction by NADPH is necessarily the first step. This reduction by NADPH is markedly biphasic, and when analyzed for two phases, rate constants of 2.46 s-1 and 0.88 s-1 are obtained at 4 degrees C, pH 7.2. The Kd (8 microM) for the binding of NADPH to the flavoprotein prior to reduction demonstrates a tight binding. Reduction by NADH also occurs and is similar in all respects to that observed with NADPH with the exception that the Kd is larger (0.167 mM) and easily measured. Oxygenatable substrates pre-equilibrated with the enzyme do not change the reduction in any way. NADP+ equilibrated with the enzyme prior to reduction removes the faster phase of the reaction leaving only the slower 0.88 s-1 phase. However, NADP+ rapidly mixed with the enzyme at the time of reduction does not affect the biphasic nature of the reduction, indicating that the binding of NADP+ to the enzyme results in a comparatively slow change of the form of the enzyme responsible for the fast phase into that which exhibits the slower rate. A primary deuterium isotope effect of approximately 6-fold has been observed on both phases of the reduction using (4R)-[4-2H]NADPH. This is strong evidence that both phases are due to primary reduction steps and that the enzyme preferentially abstracts the (4R)-proton. n-Octylamine, frequently present in turnover reactions because of its activating effect on the overall turnover rate of the enzyme, has a slightly inhibitory effect on the reduction step. We also show steady state kinetic patterns determined at both 25 degrees C and 15 degrees C which substantiate the results of Poulsen and Ziegler (J. Biol. Chem. 254, 6449-6455) which were determined at 37 degrees C.

Aniline Compounds↗
PubMed1993

Redox potentials of milk xanthine dehydrogenase. Room temperature measurement of the FAD and 2Fe/2S center potentials.

Xanthine oxidase (XO) and xanthine dehydrogenase (XDH), two forms of the same enzyme isolated from cow's milk, have differing redox potentials of their chromophores. Both XDH and XO are capable of accepting 8 electrons per active site cluster of redox acceptors. By titrating XDH with redox indicator dyes of various potentials, the potentials have been determined for the flavin as well as for the 2Fe/2S centers of the enzyme at pH 7.5, 25 degrees C. The redox potential for the FAD/FADH. half-potential was found to be -270 +/- 5 mV and that for the FADH./FADH2 half potential, -410 +/- 5 mV. The first flavin half potential is close to the value which has been reported for XO (Porras, A. G., and Palmer, G. (1982) J. Biol. Chem. 257, 11617-11626). However, the second FAD half-potential is 180 mV lower in XDH than in XO, creating a 140-mV separation between the FAD potentials in XDH. This separation gives rise to a maximum development of the flavin semiquinone in XDH near 0.9 equivalent as confirmed by EPR quantitation of FADH. formed during reductive titrations. The potentials of both the 2Fe/2S centers in XDH were determined and found to be identical to the values which were found for the iron-sulfur centers in XO.

Animals↗
PubMed1995

Rat monoamine oxidase B expressed in Escherichia coli has a covalently-bound FAD.

Rat liver monoamine oxidase B (MAO B) was expressed in E. coli as catalytically active form, though inclusion bodies of the enzyme were also formed as a major protein in the cell. The active form of the recombinant MAO B exhibited similar properties as rat liver enzyme and localized in membrane of the bacteria. Covalent attachment of FAD to polypeptide chain of the recombinant enzyme was revealed by a labeling experiment with [3H]-pargyline, an irreversible mechanism-based inhibitor, indicating that the covalent linkage of FAD to the apoprotein was formed even in the prokaryotic cell. This observation suggests autocatalytic formation of the linkage in MAO B.

Animals↗
PubMed2005

Disorders of fuel metabolism: medical complications associated with starvation, eating disorders, dietary fads, and supplements.

Disorders of fuel metabolism as they relate to abnormal fuel intake,abnormal fuel expenditure, and dietary supplements are the focus of this article. The emergency physician should be aware of the medical complications that can occur as a result of starvation states,eating disorders, fad diets, hypermetabolic states, and ergogenic aids. Knowledge and understanding of the complications associated with these disorders will facilitate the diagnosis and management of patients who present to the emergency department with any of the disorders reviewed.

Adolescent↗
PubMed2005

Diet options of obesity: fad or famous?

This article highlights the different dietary approaches that have evolved and become popular over the past few years. Whether these are fads or truly represent important changes in the way peo-ple eat and that ultimately will lead to a lower rate of obesity and improved health is impossible to know.

Body Mass Index↗
PubMed2001

Kwashiorkor in the United States: fad diets, perceived and true milk allergy, and nutritional ignorance.

BACKGROUND: Kwashiorkor is the edematous form of protein-energy malnutrition. It is associated with extreme poverty in developing countries and with chronic malabsorptive conditions such as cystic fibrosis in developed countries. Rare cases of kwashiorkor in affluent countries unrelated to chronic illness have been reported. We present 12 cases of kwashiorkor unrelated to chronic illness seen over 9 years by pediatric dermatologists throughout the United States, and discuss common causative themes in this easily preventable condition. OBSERVATIONS: Twelve children were diagnosed as having kwashiorkor in 7 tertiary referral centers throughout the United States. The diagnoses were based on the characteristic rash and the overall clinical presentation. The rash consisted of an erosive, crusting, desquamating dermatitis sometimes with classic "pasted-on" scale-the so-called flaky paint sign. Most cases were due to nutritional ignorance, perceived milk intolerance, or food faddism. Half of the cases were the result of a deliberate deviation to a protein-deficient diet because of a perceived intolerance of formula or milk. Financial and social stresses were a factor in only 2 cases, and in both cases social chaos was more of a factor than an absolute lack of financial resources. Misleading dietary histories and the presence of edema masking growth failure obscured the clinical picture in some cases. CONCLUSIONS: Physicians should consider the diagnosis of kwashiorkor in children with perceived milk allergies resulting in frequent dietary manipulations, in children following fad or unorthodox diets, or in children living in homes with significant social chaos. The presence of edema and "flaky paint" dermatitis should prompt a careful dietary investigation.

Diet Fads↗
PubMed1990

[Scientific approach in nutrition medicine and the example of diet fads].

The dietetics, seen from the historic point of view, have been more of an empirical science, yet in the past few decades they have developed a more rational, scientific basis. Unfortunately, this view is not shared by all, especially by those responsible for research policies of universities. Therefore it is not surprising that so-called "fad-diets" have gained in popularity despite the fact that these diets have not been scientifically proven as valuable. The most well known of these diets are the Schroth-, and F. X. Mayr-cure, the Evers-, Hay's, Atkins-, and Point-diet. Almost every day new diets are introduced to the public via uncritical mass media. These types of diets have nothing to do with modern throphotherapy.

Diet Fads↗
PubMed1997

Food expenditure pattern, storage practices, food fads and fallacies of seven villages of Guntur districts.

The present study was carried out to assess the food expenditure pattern, storage practices, Food fads, and fallacies of seven villages of Guntur districts. Expenditure on protective foods in Buddam village isn nil, due to which the preschool children are in Grade II and Grade III malnutrition. Introduction of weaning food to the children in all the villages is after 6 months. The most commonly used storage structure for paddy are gunny bag, puri and patra.

Anthropometry↗