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PubMed1979

Separation of unconjugated pteridines by high-pressure cation-exchange liquid chromatography.

In the course of determining the levels of unconjugated pteridines occurring in various biological fluids, such as urines, plasma and tissue culture media, a method has been developed for the separation and quantitative determination in the picomole range of ten 2-amino-4-hydroxy substituted pteridines. This method involves separation by high-pressure cation-exchange liquid chromatography and fluorescence detection of the eluted compounds at 450 nm. Optimal separation was obtained by isocratic elution with 3 mM phosphoric acid-7% methanol-1% acetonitrile at a flow-rate of 2 ml/min or with 1 mM ammonium dihydrogenphosphate pH 2.8-7% methanol-5% acetonitrile at a flow-rate of 1.5 ml/min. With either solvent, the order of elution of the compounds is: isoxanthopterin, pterin-6-carboxylic acid, xanthopterin, pterin-6-carboxaldehyde, D-erythro-neopterin, L-threo-neopterin, biopterin, 6-hydroxymethylpterin, pterin, 6-methylpterin. In addition, a systemic investigation of the effects of ammonium ion concentration and pH of the solvent as well as column temperature on the separation of these compounds was also conducted.

Cation Exchange Resins↗

PubMed1989

Biopterin and neopterin in human saliva.

Presence of biopterin and neopterin in human saliva was investigated by HPLC after iodine oxidation in acidic medium. Concentrations of biopterin and neopterin (M +/- SEM) were 1.271 +/- 0.254 and 0.358 +/- 0.075 ng per ml, respectively, in saliva of apparently healthy young male adults, ages 20 to 22 years (n = 9). Nearly identical value of the neopterin/biopterin ratio (0.29 +/- 0.07) was obtained for each of these specimens. Monapterin, the L-threo-isomer of neopterin (0.084 +/- 0.022 ng per ml saliva), and other unconjugated pterins such as xanthopterin, 6-hydroxymethylpterin and pterin were also found in the saliva. These pterins were all detectable in saliva of young female adults with similar levels to those of male saliva. Another fluorescent compound which was identical with 7-iso biopterin in retention time on HPLC was observed in all specimens of normal saliva examined.

Adult↗

PubMed1986

Pigment cell differentiation: the relationship between pterin content, allopurinol treatment, and the melanoid gene in axolotls.

The effects of allopurinol (an inhibitor of the enzyme xanthine dehydrogenase (XDH] and the melanoid gene on pigment cell differentiation in the axolotl were examined by analyzing pigment components of the xanthophore (pterins). Pterin contents of skin extracts (70% ethanol) from wild type, allopurinol-treated and melanoid axolotls were determined by thin layer chromatography (TLC) and fluorometric scanning of TLC plates. Heights of peaks produced were used as a quantitative measure for pterin content. Results reveal that melanoid animals contain significantly reduced amounts of all seven pterins examined as compared with wild type animals. Allopurinol-treated animals have reduced levels of four pterins (xanthopterin, isoxanthopterin, biopterin and sepiapterin) as compared with the wild type. These findings suggest that the alterations in pterin biosynthetic pathways, either by drug-induced inhibition of XDH activity or by the melanoid gene, produce similar dramatic changes in pigment phenotype which are manifested by alterations in pigment cell differentiation.

Allopurinol↗

PubMed1992

A comparative study of Drosophila phenylalanine hydroxylase with a natural and a synthetic tetrahydropterin as cofactor.

1. Phenylalanine hydroxylase activity has been analyzed in Drosophila melanogaster using as cofactors the natural tetrahydropteridine 5,6,7,8-tetrahydrobiopterin (H4Bip) and the synthetic one 5,6-dimethyl-5,6,7,8-tetrahydropterin (H4Dmp). 2. The apparent Vmax and KM for substrate and cofactor showed that the enzyme has two times more affinity for the substrate when H4Bip is the cofactor in the reaction. Similarly to what was found with purified rat liver phenylalanine hydroxylase, H4Bip was the most effective cofactor, leading to 4-5 times more activity than that obtained with H4Dmp. 3. With the natural cofactor H4Bip, no activation of the enzyme with Phe was necessary (in contrast to mammalian phenylalanine hydroxylase), and this tetrahydropteridine inhibits phenylalanine hydroxylase activity when the enzyme is exposed to it before phenylalanine addition. With the synthetic H4Dmp, both types of preincubations led to an increase of phenylalanine hydroxylase activity. 4. The enzyme is highly unstable compared to mammalian phenylalanine hydroxylase, even at -20 degrees C. 5. Thorax and abdomen extracts caused significant inhibition of phenylalanine hydroxylase activity from third instar larvae or newborn adult head extracts, when assayed with the synthetic cofactor H4Dmp. This inhibition did not happen with H4Bip. The presence of the pteridine 7-xanthopterin in adult bodies was not the cause of this inhibition.

Animals↗

PubMed1996

Effects of neopterin-derivatives on H2O2-induced luminol chemiluminescence: mechanistic aspects.

Neopterin, 6-D-erythro-1',2',3'-trihydroxypropyl-pterin, and its dihydroform, 7,8-dihydro-neopterin, are synthesized by human monocytes/macrophages upon stimulation by interferon-gamma. In the presence of iron chelator complexes neopterin enhances hydrogen peroxide-induced luminol chemiluminescence at neutral or slightly alkaline pH (7.5). In contrast, 7,8-dihydroneopterin scavenges chemiluminescence independently from the pH value and iron. In this study, we explored in more detail the mechanism possibly involved: analysis of the reaction products shows that 7,8-dihydroneopterin is oxidized and degraded to 7,8-dihydroxanthopterin and xanthopterin, whereas the neopterin molecule is not chemically altered during the chemiluminescence reaction. Investigations of the neopterin-induced effect show that mannitol, a scavenger of hydroxyl radicals, does not alter the enhancing effect of neopterin. L-histidine, which scavenges singlet oxygen almost as effective as hydroxyl radicals, reduces the enhancing effect of neopterin. However, singlet oxygen was not detectable during the reaction by measuring monomol light emission (1270 nm). When replacing hydrogen peroxide by 3-morpholinosydnonimine, a generator of hydroxyl radicals, or naphthalene-endoperoxide, a generator of singlet oxygen, in the luminol chemiluminescence assay, neopterin shows no enhancing effect irrespective of the presence of iron-(III)-EDTA. The data suggest that neopterin enhances hydrogen peroxide-induced luminol chemiluminescence in the presence of iron-(III)-EDTA by formation of a catalytic complex that seems to favor the formation of oxygen intermediates which derive from hydrogen peroxide and react with luminol.

Biopterins↗

PubMed1980

Quantitative determination of pterins in biological fluids by high-performance liquid chromatography.

During our continuing study of pteridine metabolism, the need arose for a more rapid and quantitative determination of pterins in biological fluids. By adopting and modifying previously developed techniques, we have obtained a rapid and sensitive method that allows the simultaneous determination of eight different pterins in human urine and blood. When examined over a 10-day period, the levels of pterins excreted by a normal individual averaged the following values expressed in picomoles per mg of creatinine: biopterin, 9104; neopterin, 6018; xanthopterin, 6561; pterin, 1136; isoxanthopterin, 636; pterin-6-carboxylate, 483; and 6-hydroxymethylpterin, 315. Moreover, 6-hydroxymethylpterin and pterin-6-carboxaldehyde were detected for the first time in the blood of normal individuals.

Chromatography, High Pressure Liquid↗

PubMed1988

Determination of pterins in urine by high-performance liquid chromatography on C18 columns conditioned with cetyltrimethylammonium bromide.

A method is proposed for the determination of pterins in urine without clean-up by reversed-phase high-performance liquid chromatography on a C18 column previously conditioned with cetyltrimethylammonium bromide. Other endogenous compounds are retained in the column, preventing interference. Xanthopterin, neopterin, isoxanthopterin, monapterin, biopterin, 6-hydroxymethylpterin, pterin and lumazine can be determined. Retention and separation mechanisms are discussed.

Cetrimonium↗

PubMed1999

Pteridine analysis in urine by capillary electrophoresis using laser-induced fluorescence detection.

Pteridines are a class of compounds excreted in urine, the levels of which are found to elevate significantly in tumor-related diseases. For the first time, we have developed a method, based on high-performance capillary electrophoresis (HPCE) and laser-induced fluorescence (LIF) detection, to monitor the pteridine levels in urine. HPCE provides better separation than high-performance liquid chromatography and the LIF detector enables us to detect minute amounts of pteridines in body fluid. Eight different pteridine derivatives were well separated in 0.1 M Tris-0.1 M borate-2 mM EDTA buffer (pH 8.75) using a 60-cm fused-silica capillary (50-micron i.d., 35-cm effective length), six of which were detected and characterized in urine samples from normal persons and different cancer patients. The detection limits of these pteridines are under 1 x 10(-10) M. The levels of neopterin, pterine, xanthopterin, and pterin-6-carboxylic acid were found to be significantly elevated in urine excreted by cancer patents, while the level of isoxanthopterin dropped in these patients. No significant change of biopterin level was found between healthy individuals and cancer patients. This method can be used in clinical laboratories either for cancer monitoring or for precancer screening.

Electrophoresis, Capillary↗

PubMed2004

Cooperative catalysis in the homodimer subunits of xanthine oxidase.

Xanthine oxidase (XOD) consists of two identical subunits. For the past 50 years or so, it was assumed that the two subunits carry out catalysis independently. Herein, we report that the presence of 6-formylpterin (6FP) or other substrates (such as xanthine or xanthopterin) at one of the two active sites affects the binding affinity and catalysis rate of 6FP at the other. When the two XOD active sites were occupied by two 6FPs simultaneously, the conversion rate (2.8 x 10(-3) s(-1)) of 6FP to 6CP is 2.95-fold faster than the conversion rate (0.95 x 10(-3) s(-1)) in the case of single 6FP bound condition. The presence of xanthine can accelerate the catalysis rate of 6FP by XOD as well as the activity-recovering rate of alloxanthine-inhibited XOD. Our experimental observations demonstrate unambiguously that the two XOD subunits are strongly cooperative in both binding and catalysis. The inhibition constant (Ki) of 6FP toward XOD was measured by a stopped-flow method to be 0.94 nM.

Binding Sites↗

PubMed1997

Photoinduced hydroxylation of deoxyguanosine in DNA by pterins: sequence specificity and mechanism.

Pterin-sensitized DNA photodamage has been characterized by a DNA sequencing technique. Exposure of double-stranded DNA to 365-nm light in the presence of pterin, 6-carboxypterin, biopterin, neopterin, and folic acid produced sequence-specific DNA lesions, whereas photoinduced DNA lesions were not observed in the presence of xanthopterin or isoxanthopterin. The DNA photodamage induced by these pterin derivatives occurred specifically at the guanine located 5' to guanine. High-pressure liquid chromatography (HPLC) analysis revealed that the pterin-sensitized DNA photodamage was predominantly due to the formation of 7,8-dihydro-8-oxo-2'-deoxyguanosine (8-oxo-dG). The DNA photodamage with pterin was not enhanced in D2O, suggesting that lO2 is not the main active species. Electron spin resonance (ESR) spin destruction experiments demonstrated that the photoexcited pterins reacted specifically with dGMP to produce pterin anion radicals. In addition, the reactivities of the photoexcited pterin derivatives with dGMP were found to correlate well with their efficiencies of DNA photodamage induction. These results indicate that the photoexcited pterins specifically oxidize deoxyguanosine in DNA to produce 8-oxo-dG through an electron transfer reaction. With denatured single-stranded DNA, the extent of pterin-sensitized photodamage was decreased and the damage occurred at most guanine residues without specificity for those located 5' to guanine. The mechanism of pterin-induced sequence-specific guanine photodamage could be explained on the basis of a recent theoretical study [Sugiyama. H., & Saito, I. (1996) J. Am. Chem. Soc. 118, 7063-7068] concerning the ionization potentials of stacked dinucleotide base pairs. Sepiapterin, a model compound for the dihydropterins, induced similar sequence-specific photolesions in double-stranded DNA. However, DNA photodamage by sepiapterin was more extensive in the presence of Cu(II), and the sites of the photolesions were different from those induced in the absence of Cu(II). These data may provide a basis for the elucidation of the molecular mechanism of solar UV carcinogenesis.

Base Sequence↗

PubMedDate not supplied

The pigments in the dorsal skin of frogs.

The five pigments 1-5 and a colorless substance 6 were present in the dorsal skin of frogs of nine selected species belonging to Rhacophoridae, Ranidae, Hylidae, and Bufonidae and were identified as pterin-6-carboxylic acid, xanthopterin, isoxanthopterin, erythro-biopterin, 6-hydroxymethylpterin, and guanine, respectively. Another pigment 7 was specifically present in the skin of genus Rhacophorus and was deduced to be a pteridine derivative composed of five molecules of pterin-6-carboxylic acid [1].

Animals↗

PubMed1998

Inhibition of xanthine oxidase by pterins.

The effect of a panel of pterins on xanthine oxidase was investigated by measuring formation of urate from xanthine as well as formazan production from nitroblue tetrazolium. The pterin derivatives, depending on their chemical structure, decreased urate as well as formazan generation: 200 microM neopterin and biopterin suppressed urate formation (90% from baseline) and formazan production (80% from baseline) as well. Their reduced forms, 7,8-dihydroneopterin and 5,6,7,8-tetrahydrobiopterin, showed a lesser but still strongly diminishing influence (40% from baseline). Another oxidized pterin namely leukopterin showed only a weak inhibitory effect. Xanthopterin, a known substrate of xanthine oxidase, had a strong effect on urate formation (80% inhibition), but a lesser effect on formazan production (30% reduction). When iron-(III)-EDTA complex was added to the reaction mixture all the effects were more pronounced. Superoxide dismutase, which removes superoxide anion by dismutation into oxygen, decreased formazan production in addition to pterin derivatives and had a small but enhancing effect on urate formation. Also the reductant N-acetylcysteine had an additive effect to pterins to diminish formazan production in a dose-dependent way. The results of our study suggest that depending on their chemical structure pterins reduce superoxide anion generation by xanthine oxidase.

Acetylcysteine↗

PubMed1965

Studies on fine structure and cytochemical properties of erythrophores in swordtail, Xiphophorus helleri, with special reference to their pigment granules (Pterinosomes).

The fine structure and the composition of pteridine pigments of erythrophores in adults of the swordtail fish, Xiphophorus helleri, were studied by means of cytochemistry, paper chromatography, ionophoresis, centrifugal fractionation, and electron microscopy. It was found that water-soluble pigments of erythrophores consisted exclusively of pteridine derivatives including large amounts of drosopterin, isodrosopterin, neodrosopterin, and moderate amounts of sepiapterin. While these substances were responsible for red pigmentation, moderate quantities of colorless pteridines, biopterin, Rana-chrome 3, xanthopterin, isoxanthopterin, and others, were also detectable. The ultrastructure of the erythrophore is characterized by numerous pigment granules and a well developed tubular endoplasmic reticulum. The former consist of a three-layered limiting membrane and inner lamellae which appear to be whorl-like due to a concentric arrangement of parallel membranes. All of the mentioned pteridines are primarily contained in this organelle which is designated, accordingly, "pterinosome." The possible functions of erythrophores and pterinosomes are discussed in the light of their structure and pigmentary constitution.

Animals↗

PubMed1952

Factors related to the growth of psittacosis virus (strain 6BC) II. Purines, pyrimidines, and other components related to nucleic acid.

In various amounts and mixtures, adenine, guanine, xanthine, hypoxanthine, thymine, thymidine, cytidylic acid, and an enzymatic digest of desoxyribonucleic acid all failed to influence the inhibition by sulfadiazine of the growth of psittacosis virus (6BC) in embryonated eggs. A number of purine analogues, including benzimidazole, 2,6-diaminopurine, and 8-azaguanine, inhibited the growth of psittacosis virus (6BC) in tissue cultures at concentrations which had no obvious toxic effects on the host tissues. The virus inhibitory action of 2,6-diaminopurine was reversed by addition of adenine and that of 8-azaguanine by guanine. The growth of psittacosis virus (6BC) was inhibited by the pteridine compounds 2-ammo-4-hydroxy-6-formylpteridine and xanthopterin, while other related substances had little or no inhibitory activity. Xanthine reversed the inhibitory effects of 2-amino-4-hydroxy-6-formylpteridine. There was no correlation between the inhibitory activity of the pteridines on xanthine oxidase and multiplication of the virus.

2-Aminopurine↗

PubMed1978

A long-term study of the excretion of folate and pterins in a human subject after ingestion of 14C folic acid, with observations on the effect of diphenylhydantoin administration.

After the administration of 2-14C folic acid to a human volunteer, urinary and fecal radioactivity, as well as urinary excretion of folate (Lactobacillus casei assay) and biopterin-like material (Crithidia fasciculata assay) were determined at intervals over a 129 day period of observation. From two 24 h urine samples erythroneopterin, bioterin, threoneopterin pterin, isoxanthopterin, and xanthopterin were isolated by chromatographic procedures, quantitated, and their specific activities were determined. The effect on the pattern of elimination of urinary radioactivity and biological activity resulting from the administration of diphenylhydantoin was studied on two occasions. Urinary radioactivity plots suggest the decay of two forms of folates with markedly different biological half lives. One short-lived (t 1/2 approximately 31.5 hr), corresponding to newly absorbed folate, and one long-lived (t 1/2 approximately 100 day) thought to represent the decay of body pools. Diphenylhydantoin does not alter the rate of elimination of the long-lived component but may accelerate losses of newly absorbed folate. The analysis of pterins does not support the hypothesis that diphenylhydantoin increases the breakdown of folates to pterins.

Adult↗

PubMed1996

Studies and comparison of pterin patterns in the plasma of dogs and cats and their alteration in various neoplasias and virus infections.

Physiological pterin levels were evaluated in plasma samples of healthy dogs and cats. Biopterin and 7-xanthopterin were determined quantitatively by HPLC after partial purification by ion exchange chromatography. Neopterin, pterin and 6-hydroxymethylpterin were not detectable in plasma samples. Pterin levels in plasma of dogs with neoplasias and cats with neoplasias or viral infections (FeLV, FIV, FIP) were determined. Dogs with various tumours did not show qualitative but distinct quantitative alterations in the pterin concentration in plasma. Biopterin concentrations in plasma of dogs after tumour exstirpation significantly decreased compared to the levels before surgery. There was only a moderate increase of the biopterin levels in plasma of cats with neoplasias in comparison to healthy animals of this species. Cats suffering from viral infections, however, showed a significant rise in biopterin concentrations. The results underscore the importance of pterins as sensitive indicators for the presence of activation of cell mediated immune response. With emphasis on biopterin the role of pterins as helpful parameters for the preventation and the monitoring of diseases is pointed out.

Animals↗

PubMed1991

Pigments and ultrastructures of pigment cells in xanthic sailfin mollies (Poecilia latipinna).

Electron micrographs of skin from xanthic (gold) sailfin mollies revealed numerous xanthophores, as well as scattered melanophores. The melanophores were seen to contain premelanosomes in various stages of development. This is consistent with the fact that xanthic mollies have been shown to be tyrosinase positive. Melanosomes in xanthic mollies appear to develop by one of two pathways: 1) from an endoplasmic reticulum-derived vesicle which develops an internal lamellar framework, and 2) by fusion of multiple Golgi-derived vesicles which lack an internal lamellar framework. Analysis of the pigments in the skin of the xanthic mollies identified four colorless pteridine pigments (xanthopterin, isoxanthopterin, neopterin, and pterin) and a carotenoid with an absorbance spectrum similar to beta-carotene. It appears that, unlike some other poeciliid fishes, sailfin mollies do not use pteridine pigments for orange coloration. Rather, they appear to rely primarily on carotenoids.

Animals↗

PubMed1989

Inhibition of the catalytic activity of bovine pineal gland hydroxyindole-O-methyltransferase (EC 2.1.1.4) by estrone, estradiol, progesterone, and testosterone but not pteridines.

The effect of pteridines and sex hormones on hydroxyindole-O-methyltransferase (HIOMT) catalysis was examined. Equivalent quantities of partially purified bovine HIOMT was incubated in the presence and absence of the various test substances and the results fitted to the Michaelis-Menten equation. The pteridines (triampterene and xanthopterin) had no noticeable effect on HIOMT catalysis, while all the sex hormones examined were found to be competitive inhibitors of the enzyme with respect to the hydroxy-substrate. Testosterone concentrations causing noticeable inhibition were above physiological while estrone, estradiol, and progesterone all caused inhibition within the physiological range; estrone was the most potent and progesterone the least potent inhibitor. The possible significance of these findings are discussed.

Acetylserotonin O-Methyltransferase↗