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PubMed1979

Anti-riboflavin activity of 8-O-alkyl derivatives of riboflavin in some Gram-positive bacteria.

Two new 8-O-alkyl derivatives of riboflavin (RF), i.e., 8-methoxy- (MOF), and 8-ethoxy-8-demethyl-D-riboflavin (EOF), their tetraacetate, and the tetraacetate of 8-hydroxy-8-demethyl-D-riboflavin (HOF) were synthesized. The anti-RF activity of MOF, EOF and HOF was estimated from the ratio CR/CI, where CI is the concentration of test flavin added to the culture medium and CR is the minimum concentration of RF needed to restore the growth inhibition. Their activity was also compared with that of roseoflavin (RoF). The decreasing order of anti-RF activity was as follows: MOF greater than RoF greater than EOF in Sarcina lutea: RoF greater than MOF greater than EOF in Bacillus cereus and Staphylococcus aureus. HOF showed no activity in any of the bacteria tested. The redox potential of these compounds decreases as follows: RF greater than RoF greater than EOF greater than MOF greater than HOF, and the RF activity of MOF and EOF could be explained by the redox potential difference between these compounds and RF.

Bacillus cereus↗
PubMed1978

[On the physiology of growth and riboflavin overproduction of Eremothecium ashbyii. III. Investigations on the incorporation of radioactive labeled substrates in cell material and riboflavin (author's transl)].

The incorporation of glycine-2-14C and adenine-U-14C in cell material and riboflavin was investigated in order to determine the proportions metabolites were channeled in growth processes and product synthesis of Eremothecium ashbyii. Extraction- and measurement methods were developed to compare the incorporation of radioactive metabolites into different cell fractions. Young cells incorporate the labeled compounds in a high rate into the cell material. With increasing age of the culture the incorporation of radioactivity is more directed to riboflavin. 96 hours old cells incorporate about seven times more 14C-adenine into riboflavin than into the cell material.

Adenine↗
PubMedDate not supplied

[Isolation of riboflavin-binding apoprotein from chicken egg protein and its use for determining riboflavin in biological samples].

A riboflavine-binding protein has been isolated from egg white and its properties have been characterized. The apoprotein-employing techniques for riboflavine detection in foods, urine, and blood serum are highly competitive with conventional labor-consuming procedures and with the high expensive HPLC method in sensitivity and selectivity, and can be recommended for riboflavine detection in biological objects.

Animals↗
PubMed1986

Biosynthesis of riboflavin. Enzymatic formation of 6,7-dimethyl-8-ribityllumazine by heavy riboflavin synthase from Bacillus subtilis.

The beta subunits of heavy riboflavin synthase catalyze the formation of 6,7-dimethyl-8-ribityllumazine from 5-amino-6-ribitylamino-2,4(1H,3H)-pyrimidinedione and a carbohydrate phosphate, Compound X. 5-Amino-6-ribitylamino-2,4(1H,3H)-pyrimidinedione 5'-phosphate is not a substrate for the enzyme, although it is an established intermediate in the biosynthesis of riboflavin. It follows that this pyrimidine phosphate must be dephosphorylated prior to the formation of 6,7-dimethyl-8-ribityllumazine.

Bacillus subtilis↗
PubMed1993

Fluorescence quenching in riboflavin-binding protein and its complex with riboflavin.

Fluorescence quenching of tryptophan residues in egg-white riboflavin-binding protein by two typical quenchers (charged iodide and uncharged acrylamide) reveals acid-induced changes of protein conformation. At neutral pH, acrylamide flow in macromolecule, (i.e., the quenching effect) is decisive; tryptophan residue accessibility for iodide is small. At low pH, some tryptophan residues are exposed to the protein surface and become more accessible to iodide. In contrast, acrylamide is less able to permeate this conformational state of RBP. Fluorescence of tryptophan residues in riboflavin-RBP complex and chemically N-bromosucinimide-modified RBP was quenched by iodide and acrylamide.

Acrylamides↗
PubMed1987

Quantification of riboflavin, riboflavin 5'-phosphate and flavin adenine dinucleotide in plasma and urine by high-performance liquid chromatography.

A high-performance liquid chromatographic method with fluorimetric detection for the quantification of riboflavin (RB), riboflavin 5'-phosphate (FMN), and flavin adenine dinucleotide (FAD) in plasma, whole blood, and urine is described. Under isocratic conditions with a reversed-phase column, the compounds are completely resolved and eluted within 9 min. Plasma proteins are precipitated with acetonitrile followed by shaking the aqueous phase with chloroform. Urine samples are diluted and injected directly. The reproducibility of this method for the quantification of RB in plasma has a between-day coefficient of variation of 6%. The application of this method is illustrated by analyzing plasma and urine samples from a human subject who received an intravenous dose of FMN equivalent to 25 mg of RB.

Adult↗
PubMed1993

Photoreactions of riboflavin with spermine and their role in tryptophan photoconsumption induced by riboflavin.

The influence of spermine (Spr) on riboflavin (Rb) and riboflavin-tryptophan (Rb-Trp) solutions irradiated at 450 nm under aerobic and anaerobic conditions was studied. In both systems, it is shown that Spr interacts with 3Rb probably giving spermine-derived and flavin-derived radicals. In the presence of oxygen, modified Rb is regenerated with the simultaneous production of the active oxygen species O2.- and/or HO2.. The addition of Spr to the Rb-Trp system under aerobic conditions leads to a small protection of Trp consumption, although oxygen consumption is increased. This small protection arises as a consequence of competitive interaction of Trp and Spr with 3Rb. The competition of Spr and oxygen for 3Rb could also explain the autocatalytic oxygen consumption observed in the presence of the amine. Under anaerobic conditions Spr produces a larger protection of Trp consumption, which is compatible with the larger Rb triplet lifetime expected under these conditions.

Animals↗
PubMed2000

Binding study of riboflavin-binding protein with riboflavin and its analogues by differential scanning calorimetry.

Thermal unfolding parameters of hens' egg-white riboflavin-binding-protein (RBP) were measured by differential scanning calorimetry. Thermal denaturation scans of apoRBP and RBP complexes with riboflavin and its analogues (FMN, N10 DL-glyceryl isoalloxazine, and N10 omega-hydroxypentyl isoalloxazine) have been measured. It was found that ligand binding causes increase of RBP thermal stability, as manifested by a change of denaturation temperature from 60.8 degrees C for apoRBP to 72.8 degrees C for RBP-Rf complex. For RBP-FMN complex, the denaturation temperature of 73.0 degrees C was even higher than for the RBP-Rf complex. The other two flavin analogues showed transition temperatures in between 66.9 degrees C and 68.8 degrees C, respectively. Analysis of excess heat capacity data showed that the best fit was the sum of two independent thermal transitions. One of the transitions, which contributed approximately 70% to the total heat effect, has transition temperature in the broad range of 60.5-73.2 degrees C; the other transition temperature is in the narrower range of 65.4-71.1 degrees C. The observed transitions can be related to RBP domains.

Calorimetry, Differential Scanning↗
PubMed2000

Riboflavin phosphorylation is the crucial event in riboflavin transport by isolated rat enterocytes.

In isolated rat enterocytes, both normoenergized (normal) and de-energized with rotenone, riboflavin intracellular metabolic processes, operating in association with a membrane-specific transport mechanism, were investigated. The contents of unlabeled (endogenous) and labeled (exogenous) flavins [riboflavin (RF), flavin mononucleotide (FMN), flavin adenindinucleotide (FAD)] were determined by HPLC before and after incubation with tritiated RF. In normoenergized enterocytes, total labeled RF content (i.e., total uptake, the sum of RF membrane transport and intracellular metabolism) increased steadily to a plateau after 20 min incubation; FMN and FAD contents reached a plateau between 3 and 20 min, whereas free RF content increased constantly. The phosphorylated forms prevailed over the free form ( approximately 60% of total flavins). In de-energized enterocytes, RF total uptake was significantly lower than in normoenergized enterocytes and reached a plateau after only 3 min incubation. FMN and FAD contents were significantly lower than in normoenergized enterocytes, and free RF represented the prevailing form of flavins (70% of total RF ). In both normoenergized and de-energized enterocytes, the contents of unlabeled total RF, FMN and FAD decreased significantly after 20 min incubation, whereas free RF increased significantly only in normoenergized enterocytes. After 20 min incubation, the RF structural analog 8-dimethyl-amino-8-demethyl-RF caused a significant decrease of all flavin contents, whereas 5'-deoxy-RF decreased only the total and free RF contents. Results directly confirmed the leading role of metabolic processes such as phosphorylation in RF transport by isolated small intestinal enterocytes.

Animals↗
PubMed2002

The pyrimidine nucleotide reductase step in riboflavin and F(420) biosynthesis in archaea proceeds by the eukaryotic route to riboflavin.

The Methanococcus jannaschii gene MJ0671 was cloned and overexpressed in Escherichia coli, and its gene product was tested for its ability to catalyze the pyridine nucleotide-dependent reduction of either 2,5-diamino-6-ribosylamino-4(3H)-pyrimidinone 5'-phosphate (compound 3) to 2,5-diamino-6-ribitylamino-4(3H)-pyrimidinone 5'-phosphate (compound 4) or 5-amino-6-ribosylamino-2,4(1H,3H)-pyrimidinedione 5'-phosphate (compound 7) to 5-amino-6-ribitylamino-2,4(1H,3H)-pyrimidinedione 5'-phosphate (compound 5). Only compound 3 was found to serve as a substrate for the enzyme. NADPH and NADH functioned equally well as the reductants. This specificity for the reduction of compound 3 was also confirmed by using cell extracts of M. jannaschii and Methanosarcina thermophila. Thus, this step in riboflavin biosynthesis in these archaea is the same as that found in yeasts. The absence of the other genes in the biosynthesis of riboflavin in Archaea is discussed.

Archaeal Proteins↗
PubMed1988

Riboflavin-binding protein from reptiles: a comparison with avian riboflavin-binding proteins.

1. Riboflavin-binding protein (RBP) has been isolated for the first time from reptilian sources. 2. RBP from eggs of Python molurus (Indian python) and Chrysemys picta (painted turtle) has been isolated and compared to RBP from Gallus gallus domesticus (chicken), a well-characterized protein, and a newly isolated RBP from Cairina moschata (Muscovy duck). 3. Each of the proteins is phosphorylated and glycosylated. 4. The ratio of riboflavin binding to protein is 1:1 and the KD for each protein is between 1-3 nM. 5. The mol. wts, different for each species, range from 30,000-40,000, with the reptilian proteins being approx. 10,000 larger than the avian proteins.

Amino Acids↗
PubMed1994

Termination of pregnancy in mice following administration of antibodies to the pentadecapeptide 10-24 of chicken riboflavin carrier protein: identification of a bioneutralizing epitope of chicken riboflavin carrier protein.

Our studies have shown that the administration of antibodies to chicken riboflavin carrier protein (cRCP) or disulfide-reduced carboxymethylated cRCP (RCM-RCP) leads to termination of pregnancy in mice. In an attempt to delineate the bioneutralizing epitopes, a combination of chemical modification and predictive methods was used. The results led to the identification of the region 10-24 of cRCP as a potential candidate. A single injection of antipeptide antibodies to pregnant mice on day 11 resulted in 100% pregnancy termination. This was accompanied by a drastic reduction in circulatory progesterone as early as 24 h after the antibody administration. These results thus demonstrate that the amino acid sequence 10-24 of cRCP harbours a bioneutralizing epitope of cRCP.

Abortion, Spontaneous↗
PubMed1997

Fungal riboflavin 5'-hydroxymethyl dehydrogenase catalyzes formation of both the aldehyde (riboflavinal) and the acid (riboflavinoic acid).

The purified enzyme from Schizophyllum commune that readily catalyzes the oxidation of the 5'-hydroxymethyl function of riboflavin (vitamin B2) with a redox dye and O2 to form the 5'-aldehyde can more slowly further oxidize the 5'-aldehyde to the 5'-acid. Hence, the formation of these so-called 'schizoflavins' can be accounted for by the action of one enzyme.

Alcohol Oxidoreductases↗
PubMed2000

Analysis of riboflavin and riboflavin cofactor levels in plasma by high-performance liquid chromatography.

We describe an assay which determines simultaneously riboflavin (RF), flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD) in plasma, using galactoflavin (GF) as an internal standard. The flavins were extracted on a C18 Sep-Pack cartridge after protein precipitation with 10% trichloroacetic acid, and were analyzed on a C18 RP-HPLC with 85% phosphate-magnesium acetate buffer (pH 3.4) and 15% acetonitrile. FAD, FMN, GF and RF extraction recoveries were 101.0-5.6, 97.0-6.5, 97.0-2.0 and 95.0-4.1%, and reproducibilities were 5.9, 6.8, 2.1 and 4.3%, respectively. FAD, FMN and RF values in infant and adolescent plasma were in the range 53.5-108.2, 9.0-25.1 and 12.7-53.4 nM, and 36.5-157.20, 7.1-24.6 and 8.2-57.8 nM, respectively. Using GF as an internal standard improved the quantification of these B2 vitamers.

Adolescent↗
PubMed1977

[Active transport of riboflavin in the yeast Pichia guilliermondii. Detection and some properties of the cryptic riboflavin permease].

In contrast to cells and protoplasts of the wild strain intact cells and protoplasts of riboflavin (RF)-deficient mutants of Pichia guilliermondii yeast possessing multiple sensitivity to antibiotics and antimetabolites were found capable to accomplish active transport of RF. The accumulation of RF against concentration gradient was energized by endogenous energy sources and was strongly depressed by uncouplers of oxidative phosphorylation and by inhibitors of respiration. RF transport was also blocked by the agents which destroy the permeability barrier and by sucrose. Cyclohemide did not inhibit the transport of vitamin B2. Uptake of RF depends on temperature and pH of the incubation mixture. RF permease possessed rather stringent substrate specificity and did not catalyze transport of FMN and FAD. RF uptake in two strains tested, MS1-3 and MS1, followed saturation kinetics (Km = 0.17 mM and 2.0 mM, respectively) and was not connected with RF auxotrophy. The ability for exogenous RF uptake was controlled by recessive allele. Restoration of normal resistance to antibiotics and antimetabolites was accompanied by a decrease in the permease affinity for substrate.

Alleles↗
PubMed1995

Sequence of a cDNA encoding turtle riboflavin-binding protein: a comparison with avian riboflavin-binding protein.

To search for the existence and distribution of a riboflavin-binding protein (RfBP), total RNA from estrogen-treated oviparous animals were screened by Northern hybridization using chicken RfBP cDNA as a probe. Besides avian livers and oviducts, RfBP mRNA was found in turtle liver, but not in the turtle oviduct. To elucidate the structure of the RfBP from a reptilian source, we constructed a cDNA library from estrogen-injected turtle liver, and a full-length turtle RfBP-encoding cDNA was cloned and sequenced. The open reading frame (ORF) encoded 242 amino acids (aa) including a signal peptide of 18 aa. There is an overall 71.3% aa identity between the deduced aa sequences of turtle and chicken. The aa sequence of turtle and chicken RfBP also show more than 30% similarity to a fragment of folate-binding protein (FBP). Six Trp and nine pairs of Cys residues are conserved between the two RfBPs with only one pair of Cys residues missing in FBP. The two Asn-linked glycosylation sites found in chicken RfBP are conserved in turtle RfBP, but only one of which is conserved in FBP. However, there is an additional potential N-glycosylation site in the turtle sequence and this may provide a better explanation for the greater molecular weight of the turtle protein than chicken RfBP. Turtle RfBP contains a region of nine Ser and five Glu residues which is present in mature chicken RfBP as eight phosphorylserine clusters forming a highly anionic region at the C terminus, but this region is not found in FBP.

Amino Acid Sequence↗
PubMed1984

Characterization of hen egg white- and yolk-riboflavin binding proteins and amino acid sequence of egg white-riboflavin binding protein.

White- and Yolk-riboflavin binding proteins were isolated from hen eggs, and characterized as to their chemical properties. White- and Yolk-RBPs had almost same amino acid compositions except for glutamic acid, but their carbohydrate compositions were different from each other. The complete amino acid sequence of White-RBP was determined by conventional methods. White-RBP comprised 219 amino acid residues, and the amino-terminus was pyroglutamic acid (pyrrolidonecarboxylic acid). Two amino acids, lysine and asparagine, were found at the fourteenth residue from the amino-terminus. Carbohydrate chains were linked to asparagine residues at positions 36 and 147. Both White- and Yolk-RBPs were phosphorylated. In White-RBP either six or seven of nine serine residues between Ser(185) and Ser(197) were phosphorylated. The amino acid sequences around phosphoserines showed that phosphorylation might occur at a serine residue in one of the following sequences; Ser-X-Glu or Ser-X-Ser(P).

Amino Acid Sequence↗