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PubMed1979

Purification of riboflavin-binding proteins from bovine plasma and discovery of a pregnancy-specific riboflavin-binding protein.

Riboflavin-binding proteins have been purified from bovine plasma using flavinyl agarose beads. At least three major protein bands, migrating in regions assigned to the beta- and gamma-globulins of plasma, are observed by cellulose acetate electrophoresis. These proteins coelute from a calibrated Sephadex G-100 column in the volume corresponding to a molecular weight of approximately 150,000; a small amount of another riboflavin-binding protein (molecular weight approximately 37,000) is also present. Polyacrylamide gel electrophoresis of the proteins, with detection by autoradiography of those having tightly bound [2-14C]riboflavin, reveals one protein band which is present only in preparations from pregnant cows. This protein has been purified to apparent homogeneity by storing the mixture of riboflavin-binding proteins at 8 degrees C for 3 weeks, which precipitates the other, less stable proteins. Hence, bovine plasma, like that of the laying hen, contains a number of riboflavin-binding proteins, one of which correlates with pregnancy.

Animals↗

PubMed1980

[Effect of methionine supplementation of a diet low in riboflavin and at 2 levels of protein on metabolism of riboflavin in the lactating rat].

Lactating female rats were fed diets A or B containing 18 and 12% of casein respectively, or similar diets but supplemented with 0.4% of methionine (diets AM or BM). The animals and their pups were sacrificed at the 18th day of lactation. Control non lactating female rats fed the same diets for the same period of time were also sacrificed. Total riboflavin and its various forms (flavin adenin dinucleotide, flavin mononucleotide + free riboflavin) were measured in various tissues as well as in the milk which was collected from the stomach of the pups after a time controlled suck. In the lactating females fed diets A and B as well as in the control animals fed the same diets the concentrations of riboflavin and of its various forms in plasma, liver and carcass are unchanged. However in group B, they are higher in milk and in tissues of the pups. These results seem to be due to a decrease in food intake by the lactating females fed diet B which results in a decrease in milk production which in turn induces a lower growth rate of the pups although the riboflavin consumption by the latter is unchanged. Addition of methionine to the diet B (diet BM) induces the same effects as diet A which contains the highest amount of proteins but addition of methionine to the diet A (diet AM) has no further incidence. Therefore the present study has not revealed any direct effect of methionine on riboflavin metabolism in lactating female rats and their pups since the effects are similar to an increase of the total protein level in the diet. In both cases they seem to be simply related to an increase of the food consumption.

Animals↗

PubMed1976

Regulation of 6-hydroxy-2,4,5-triaminopyrimidine synthesis by riboflavin and iron in riboflavin-deficient mutants of Pichia guilliermondii yeast.

The effect of riboflavin and iron on 6-hydroxy-2,4,5-triaminopyrimidine synthesis rate was investigated in the cultures of the yeast Pichia guilliermondii (rib2 mutants) with the blocked second reaction to flavinogenesis. It was shown that riboflavin inhibited the 6-hydroxy-2,4,5-triaminopyrimidine synthesis rate in iron-rich and iron-deficient cells of mutants with low riboflavin requirements. Cycloheximide did not prevent the stimulation of 6-hydroxy-2,4,5-triaminopyrimidine synthesis caused by riboflavin starvation. 7-methyl-8-trifluoromethyl-10-(1'-D-ribityl)isoalloxazine strongly inhibited the 6-hydroxy-2,4,5-triaminopyrimidine synthesis, while 7-methyl-8-trifluoro-methyl-10-(beta-hydroxyethyl)izoalloxazine and galactoflavin exerted only a slight effect on this process. The 6-hydroxy-2,4,5-triaminopyrimidine synthesis rate in iron-deficient cells was significantly higher than in iron-rich cells. The 2,2'-dipyridyl treatment of iron-rich cells caused the stimulation of 6-hydroxy-2,4,5-triaminopyrimidine synthesis and cycloheximide abolished this effect. The results suggest that the activity of the first enzyme of flavinogenesis (guanylic cyclohydrolase) is under the control of feedback inhibition by flavins and the biosynthesis of this enzyme is regulated by iron.

2,2'-Dipyridyl↗

PubMed1987

Isolation of riboflavin carrier proteins from pregnant human and umbilical cord serum: similarities with chicken egg riboflavin carrier protein.

A riboflavin carrier protein has been purified from human pregnancy and umbilical cord sera by affinity chromatography and fast protein liquid chromatography. This protein has a similar molecular weight to the chicken egg riboflavin carrier protein and shares other physicochemical properties, such as pI and riboflavin binding characteristics, with the avian counterpart. A high degree of immunological cross-reactivity is observed between the human and avian riboflavin binding proteins indicating the extensive conservation of this protein throughout evolution.

Animals↗

PubMed1988

Interaction of riboflavin binding protein with riboflavin, quinacrine, chlorpromazine and daunomycin.

1. circular dichroism and fluorescence measurements were used to study the reversible unfolding of riboflavin-riboflavin binding protein complex. Both methods showed that the complex was unfolded according to the two-state model. 2. The results suggest that riboflavin was strongly bound in the hydrophobic cleft of the protein and that it could not be dislodged by TFE, MeOH or SDS without major unfolding of the unique tertiary structure of the protein. 3. In addition, it has been also shown that quinacrine, chlorpromazine and daunomycin did not form stereospecific complexes with riboflavin binding protein.

Carrier Proteins↗

PubMed1983

Multiple acyl-CoA dehydrogenase deficiency occurring in pregnancy and caused by a defect in riboflavin metabolism in the mother. Study of a kindred with seven deaths in infancy: Value of riboflavin therapy in preventing this syndrome.

Seven infants in one kindred died: one was stillborn; the others, who were floppy at birth and were breast-fed, developed a disorder with the odor of sweaty feet and died in early infancy. In two further pregnancies, 3-hydroxvisovaleric, glutaric, and C6-C10-dicarboxylic acids were demonstrated in the mother's urine during the seventh month. Riboflavin therapy in the last trimester of pregnancy and a riboflavin-rich diet given the infants prevented this syndrome. The presence of abnormal erythrocyte glutathione-reductase activity in the mother while she excreted normal amounts of riboflavin in her urine indicates a probable disorder of riboflavin metabolism resulting in multiple acyl-CoA dehydrogenase deficiency.

Acyl-CoA Dehydrogenases↗

PubMed1978

Resonance Raman spectra of riboflavin and its derivatives in the bound state with egg riboflavin binding proteins.

The resonance Raman spectra of riboflavin (RF) and its derivatives, including 3-deuterated (3-D RF), 3-methyl (3-CH3 RF), 3-carboxymethyl (3-CH2COOH RF), and 7,8-dichlororiboflavins (7,8-Cl RF), in H2O and D2O were observed in the 700-1700 cm-1 region. The fluorescence problem of riboflavin was overcome by complex formation of riboflavin with riboflavin binding proteins. The observed frequencies of Raman lines of RF are in good agreement with those of glucose oxidase obtained by Spiro et al. by the resonance CARS method, although the present spectral range is extended to much lower frequency with a higher signal-to-noise ratio than that for glucose oxidase. The observed Raman lines were assigned to the individual ring modes of isoalloxazine on the basis of the Raman spectra of appropriate model compounds such as uracil, pyrazine, and o-xylene. The 1253 cm-1 line of RF was shifted to ca. 1300 cm-1 for 3-D RF, 3-CH3 RF, and 3-CH2COOH RF, and accordingly can be assigned to the CN stretching mode of Ring III. The 1632 cm-1 line of RF was shifted for 7,8-Cl RF and was assigned to a Ring I mode. No Raman line mainly due to C = O stretching mode was observed in the present resonance Raman spectra.

Carrier Proteins↗

PubMed1982

Thermodynamics of association of egg yolk riboflavin binding protein with 8-substituted riboflavins. Comparison with the egg white protein.

The association constants of hen egg yolk riboflavin binding protein with 8-substituted riboflavins were measured using a fluorometric titration method in the range of 10-40 degrees C, and thermodynamic parameters were calculated using ordinary methods. The flavins used were riboflavins whose 8-methyl group was substituted with HRN, RR'N, RO type groups, or halogen atoms. From a plot of delta H degrees against delta Su (unitary entropy change), the flavins were classified into four groups, i.e., HRN, RR'N, RO, and halogen type substituents. In each group, the linear free energy relationship, delta H degrees = u . delta Su+v (u and v were constants specific for each group), was found to be similar to that for egg white riboflavin binding protein, though with different specific constants for each egg protein. The relation between delta Su and the bulkiness (molecular volume) of 8-substituents suggested burying of the 8-substituents in a cavity of the protein similar to that of the egg white protein, but of smaller volume. The behavior of the halogen group was similar to that of the other three groups, and could be explained in terms of the bulkiness of the substituents rather than by assuming electric repulsion between halogen substituents and the binding site, which is in contrast with the case of egg white protein. A linear relation between v value and the wavelength of the visible absorption peak of flavins wa also found.

Animals↗

PubMed1995

Fluorometric riboflavin titration in plasma by riboflavin-binding apoprotein as a method for vitamin B2 status assessment.

A method for plasma riboflavin determination by riboflavin-binding apoprotein titration has been proposed for vitamin B2 status evaluation. The method is based on the formation of riboflavin-apoprotein complex accompanied by full loss of fluorescence peculiar to free riboflavin. The data obtained have demonstrated a correlation with indicators of the vitamin B2 status such as urinary excretion, erythrocyte content, and stimulation of the glutathione reductase activity by flavin adenine dinucleotide. Levels > 6 ng/ml blood plasma may be considered to be a criterion for normal vitamin B2 supply.

Adolescent↗

PubMed1991

Riboflavin carrier protein from carp (C. carpio) eggs: comparison with avian riboflavin carrier protein.

A protein exhibiting immunological cross-reactivity with the chicken egg-white riboflavin carrier protein was detected by radioimmunoassay in the eggs and serum of the fresh water fish Cyprinus carpio and subsequently purified to homogeneity by use of affinity chromatography. Fish riboflavin carrier protein resembled chicken riboflavin carrier protein with respect to most of its physicochemical characteristics. The major epitopes of chicken riboflavin carrier protein were shown to be conserved in the fish protein as probed with monoclonal antibodies to the avian vitamin carrier.

Animals↗

PubMed1991

Urinary riboflavin and its metabolites: effects of riboflavin supplementation in healthy residents of rural Georgia (USA).

The following study was designed to provide a comprehensive assessment of urinary riboflavin and flavin metabolites before and after ingestion of a riboflavin load in normal human volunteers. With respect to riboflavin, the total flavin excretion, the flavin-to-creatinine ratio, and the response of the flavin catabolites to the supplement indicate a well-nourished population. Differences in the effects of supplementation on the specific flavin catabolites across sex and age groups are included in detail for the first time. The feasibility of the use of flavin catabolites for determination of riboflavin status should be tested further in individuals with clinical signs of ariboflavinosis.

Adolescent↗

PubMed1988

Riboflavin status and photo-induced riboflavin binding to the proteins of the rat ocular lens.

The presence of radioactivity in lenses of rats injected intraperitoneally with a solution of tryptophan and 14C-riboflavin, irradiated during 48 hours and under N2 atmosphere, was detected. The excitation fluorescence spectrum (lambda emission = 520 nm) of the soluble lens fraction corresponds to the riboflavin decomposition product of lumichrome type. When 14C-riboflavin enriched lenses were exposed to visible light, a photo-induced binding between riboflavin and a water insoluble protein fraction of the lenses was observed. This finding may help to clarify the lens modifications during aging and in cataractogenesis.

Animals↗

PubMed1978

Biosynthesis of riboflavin. 6,7-Dimethyl-8-ribityllumazine 5'-phosphate is not a substrate for riboflavin synthase.

Phosphotransferase from carrot is shown to catalyze the phosphorylation of 6,7-dimethyl-8-ribityllumazine specifically at position 5' of the ribityl side chain. The lumazine 5'-phosphate is neither a substrate nor an inhibitor of riboflavin synthase from Bacillus subtilis and Escherichia coli. It follows that the obligatory product of riboflavin synthase is riboflavin and not FMN.

Bacillus subtilis↗

PubMed1982

Lipid metabolism in riboflavin-deficient rats. 1. Effect of dietary lipids on riboflavin status and fatty acid profiles.

1. The increase in activation coefficient (stimulated: basal activity) of erythrocyte NAD(P)H2: glutathione oxidoreductase (EC 1.6.4.2) and reduction in hepatic flavin concentration which occurred in riboflavin-deficient weanling rats were not markedly or consistently affected by differences in the concentration of lipid in the diet nor by differences in the total proportion of saturated or polyunsaturated fatty acids in the dietary lipid. 2. Their gain in body-weight was, however, reduced when the dietary lipid concentration was increased from 30 to 200 g/kg and liver: body-weight and hepatic triglyceride content were correspondingly increased, suggesting a functionally-deleterious effect of high fat intake in the deficient animals. This was especially severe when the diets contained cottonseed oil, which appeared to be toxic for the deficient animals. 3. Comparisons between fatty acid profiles of hepatic phospholipids of deficient, pair-fed and ad lib,-fed control animals indicated that the increase in proportion of 18:2 omega 6 and the decrease in proportion of 20:4 omega 6 observed in deficient animals were due specifically to riboflavin deficiency, whereas certain other changes were probably caused by inanition. The changes in 18:2 omega 6 and 20:4 omega 6 were observed at both low and high levels of lipid intake and at both low and high levels of dietary lipid polyunsaturation. Similar changes in fatty acid profiles were observed in renal, erythrocyte membrane, and plasma phospholipids, but were not seen in cardiac phospholipids, 4. A consistent increase in proportion of 18:2 omega 6 was also observed in the hepatic triglycerides, together with a decrease in proportion of 16:0. 5. It is concluded that acute riboflavin deficiency affects lipid metabolism in a characteristic manner, probably by interfering with beta-oxidation of fatty acids, but that diets of high lipid content do not significantly increase the extent of flavin depletion.

Animals↗

PubMed2006

Riboflavin analogs and inhibitors of riboflavin biosynthesis.

Flavins are active components of many enzymes. In most cases, riboflavin (vitamin B(2)) as a coenzyme represents the catalytic part of the holoenzyme. Riboflavin is an amphiphatic molecule and allows a large variety of different interactions with the enzyme itself and also with the substrate. A great number of active riboflavin analogs can readily be synthesized by chemical methods and, thus, a large number of possible inhibitors for many different enzyme targets is conceivable. As mammalian and especially human biochemistry depends on flavins as well, the target of the inhibiting flavin analog has to be carefully selected to avoid unwanted effects. In addition to flavoproteins, enzymes, which are involved in the biosynthesis of flavins, are possible targets for anti-infectives. Only a few flavin analogs or inhibitors of flavin biosynthesis have been subjected to detailed studies to evaluate their biological activity. Nevertheless, flavin analogs certainly have the potential to serve as basic structures for the development of novel anti-infectives and it is possible that, in the future, the urgent need for new molecules to fight multiresistant microorganisms will be met.

Animals↗

PubMed1982

Thermodynamics of association of 8-substituted riboflavins with egg white riboflavin binding protein.

Association constants of 14 species of riboflavin derivatives with hen egg-white riboflavin binding protein were measured by a fluorometric titration method using flavin and protein fluorescence in a temperature range of 10--42 degrees C. The derivatives were riboflavins whose 8-CH3 group was substituted with alkylamino, alkyloxy, halogen or hydrogen. The flavin derivatives were classified into four groups, i.e., RR'N, HRN, RO, and halogen, on the basis of the linear relation between enthalpy and entropy changes (linear free energy relationship), and from the chemical structures of the 8-substituents. The relation between the entropy change and the bulkiness of 8-substituents suggested burying of the substituents in a cavity of the protein, and provided an indication of the size of the substituent-accepting cavity. The relation also suggested an electric repulsion between halogen substituents and the binding site. A very good correlation was found between the constant term of the linear free energy relation and the wavelength of the visible absorption peak of flavins, and this correlation suggested the electronic nature of the flavin-protein interaction.

Carrier Proteins↗

PubMed1999

The ribR gene encodes a monofunctional riboflavin kinase which is involved in regulation of the Bacillus subtilis riboflavin operon.

A 3.5 kb EcoRI-BamHI fragment of Bacillus subtilis chromosomal DNA carrying the ribR gene, involved in regulation of the B. subtilis riboflavin operon, was cloned in the B. subtilis-Escherichia coli shuttle vector pCB20. DNA sequence analysis of this fragment revealed several ORFs, one of which encodes a polypeptide of 230 amino acids with up to 45% sequence identity with FAD synthetases from a number of micro-organisms, such as Corynebacterium ammoniagenes, E. coli and Pseudomonas fluorescens, and also to the ribC gene product of B. subtilis. The ribR gene was amplified by PCR, cloned and expressed in E. coli. Measurement of flavokinase activity in cell extracts demonstrated that ribR encodes a monofunctional flavokinase which converts riboflavin into FMN but not to FAD, and is specific for the reduced form of riboflavin.

Amino Acid Sequence↗

PubMed1986

Riboflavin responsive multiple acyl-CoA dehydrogenation deficiency. Assessment of 3 years of riboflavin treatment.

A boy with riboflavin-responsive beta-oxidation deficiency (multiple acyl-CoA dehydrogenation deficiency) was assessed clinically and biochemically after 3 years of continuous riboflavin medication. He was diagnosed at the age of three years after an attack of a Reye's syndrome-like disease. During the 3 years of assessment he has experienced no serious disease; although short episodes of fatigue and loss of appetite have been noted. His mental and physical development has been normal. Biochemically the abnormal excretion of organic acid metabolites, characteristic of the acyl-CoA dehydrogenation deficiency, has been continuously present. Quantitatively there has been a trend to a more simple picture with ethylmalonic acid as the predominant metabolite. However, because of the large within-day variation in the excretion of all the metabolites, changes following diet and riboflavin trials must be interpreted with caution in these patients.

Acyl Coenzyme A↗