Pigment patterns in mutants affecting the biosynthesis of pteridines and xanthommatin in Drosophila melanogaster

Eye-color mutants of Drosophila melanogaster have been analyzed for their pigment content and related metabolites. Xanthommatin and dihydroxanthommatin (pigments causing brown eye color) were measured after selective extraction in acidified butanol. Pteridines (pigments causing red eye color) were quantitated after separation of 28 spots by thin-layer chromatography, most of which are pteridines and a few of which are fluorescent metabolites from the xanthommatin pathway. Pigment patterns have been studied in 45 loci. The pteridine pathway ramifies into two double branches giving rise to isoxanthopterin, drosopterins, and biopterin as final products. The regulatory relationship among the branches and the metabolic blockage of the mutants are discussed. The Hn locus is proposed to regulate pteridine synthesis in a step between pyruvoyltetrahydropterin and dihydropterin. The results also indicate that the synthesis and accumulation of xanthommatin in the eyes might be related to the synthesis of pteridines.Support for this work was provided to J.F. in part by a grant from the Ministerio de Universidades e Investigación (Spain) and to F.J.S. by a grant from the Ministerio de Educación y Ciencia (Spain).     

Mechanism of suppression in Drosophila. V. Localization of the purple mutant of Drosophila melanogaster in the pteridine biosynthetic pathway

The suppressible eye color mutant purple (pr) of Drosophila melanogaster is known to be unable to synthesize a wild-type complement of pteridine eye pigments. This study measures the reduced levels of drosopterins, sepiapterin, and an unidentified presumed pteridine in pr and pr ^bw. Pteridine analyses in double mutants combining pr with one of three other eye color mutants sepia, Henna-recessive³, and prune², suggest that the metabolic block in pr occurs prior to sepiapterin biosynthesis. Measurements of GTP and GTP cyclohydrolase in pr showed wild-type levels and indicate the metabolic block in pr to be at one of the steps converting dihydroneopterin triphosphate to sepiapterin. Quantitation of pteridines in suppressed purple [su(s) ²; pr and pr; su(pr) ^e3] shows restoration of pteridines to wild-type or nearly wild-type levels.T. G. W. is a predoctoral trainee supported by Grant GM 1974 from the National Institute of General Medical Sciences, National Institutes of Health.The Oak Ridge National Laboratory is operated by Union Carbide Corporation for the U.S. Energy Research and Development Administration.     

Quantification and excretion profiles of pteridines in primate urine.

Biopterin, 6-hydroxymethyl-pterin, isoxanthopterin, neopterin and, pterin were quantified in stress-free collected spontaneous morning urine samples from Callithrix jacchus, Saguinus fuscicollis, Saguinus labiatus, Saimiri sciureus, Presbytis entellus, Cercopithecus albogularis, Cercocebus torquatus, Macaca fascicularis, Hylobates concolor, Pongo pygmaeus, and Gorilla gorilla. In most species, biopterin was the most frequent urinary pteridine followed by neopterin. Sex differences in biopterin and neopterin excretion were observed in Gorilla gorilla and Pongo pygmaeus. Pterin and isoxanthopterin were only present in minor concentrations. 6-hydroxymethyl-pterin was barely detectable and not present in the urine of Saguinus labiatus, Saimiri sciureus, and both male Gorilla gorilla and Pongo pygmaeus.     

Purification and properties of the enzymes from Drosophila melanogaster that catalyze the synthesis of sepiapterin from Dihydroneopterin triphosphate

Sepiapterin synthase, the enzyme system responsible for the synthesis of sepiapterin from dihydroneopterin triphosphate, has been partially purified from extracts of the heads of young adult fruit flies (Drosophila melanogaster). The sepiapterin synthase system consists of two components, termed enzyme A (MW 82,000) and enzyme B (MW 36,000). Some of the properties of the enzyme system are as follows: NADPH and a divalent cation, supplied most effectively as MgCl₂, are required for activity; optimal activity occurs at pH 7.4 and 30 C; the K _m for dihydroneopterin triphosphate is 10 µm; and a number of unconjugated pterins, including biopterin and sepiapterin, are inhibitory. Dihydroneopterin cannot be used as substrate in place of dihydroneopterin triphosphate. Evidence is presented in support of a proposed reaction mechanism for the enzymatic conversion of dihydroneopterin triphosphate to sepiapterin in which enzyme A catalyzes the production of a labile intermediate by nonhydrolytic elimination of the phosphates of dihydroneopterin triphosphate, and enzyme B catalyzes the conversion of this intermediate, in the presence of NADPH, to sepiapterin. An analysis of the activity of sepiapterin synthase during development in Drosophila revealed the presence of a small amount of activity in eggs and young larvae and a much larger amount in late pupae and young adults. Sepiapterin synthase activity during development corresponds with the appearance of sepiapterin in the flies. Of a variety of eye color mutants of Drosophila melanogaster tested for sepiapterin synthase activity, only purple (pr) flies contained activity that was significantly lower than that found in the wild-type flies (22% of the wild-type activity). Further studies indicated that the amount of enzyme A activity is low in purple flies, whereas the amount of enzyme B activity is equal to that present in wild-type flies.This work was supported by research grants from the National Institutes of Health (AM03442) and the National Science Foundation (PCM75-19513 A02). G. G. K. was supported as a predoctoral trainee by National Institutes of Health Training Grant GM00515.     

Gch在喋啶代谢通路中参与鱼类体色形成的研究

鸟苷三磷酸环化水解酶 (GTP cyclohydrolase,Gch)是具有GTP-cyclohydro结构域的蛋白酶,广泛存在于脊椎动物和无脊椎动物中。哺乳动物和鸟类中只具有Gch1,硬骨鱼类和两栖动物中Gch1存在旁系同源的Gch2和Gch3,且功能存在差异。Gch是以鸟苷三磷酸为底物,最终形成四氢生物蝶呤(tetrahydrobiopterin,BH4)的限速酶,而BH4是芳香族氨基酸羟化酶必须的辅助因子,参与多种激素和神经递质的合成。Gch是催化各种蝶呤生物合成的起始步骤,例如皮肤色素、眼色素、甲氨蝶呤、叶黄酸和BH4等,在体内一系列生理病理过程中发挥重要作用。Gch的生理功能与BH4的生物合成有着不可分割的联系,作为BH4生物合成的唯一限速酶,其活性可作为神经元和色素细胞的发育指示物,也是研究色素形成和神经递质生物合成的重要标志。目前,Gch在肿瘤和心血管等疾病的发病机制方面已获得广泛关注和解析,而色素合成和体色调控的作用研究多集中在昆虫方面,在硬骨鱼类中较少。因此,本文将重点对Gch基因、蛋白质、功能以及在鱼类体色方面中的作用进行总结归纳,对深入分析Gch在鱼类体色形成中的作用及后期鱼类体色改良具有重要的指导意义。     

Proximate mechanisms of colour variation in the frillneck lizard: geographical differences in pigment contents of an ornament

Animal coloration has evolved in contexts such as communication, camouflage, and thermoregulation. Most studies of animal coloration focus on its adaptive benefits, whereas its underlying mechanisms have received less attention despite their potential influence on adaptive benefits. In fish and reptiles, for example, colour variation from yellow to red can be produced by carotenoid and/or pteridine pigments, which differ dramatically in the way they are obtained (carotenoids through diet and pteridines synthesized de novo). Hence, potential adaptive benefits could differ greatly depending on the relative contribution to coloration of different pigments. In the present study, we investigate the mechanisms underlying colour variation in the frill of the Australian frillneck lizard (Sauropsida: Chlamydosaurus kingii). Frill colour varies between populations across the species' range (red, orange, yellow or white). We argue that this geographical variation results from different concentrations of carotenoids and pteridines in the frill. Frill carotenoid concentrations were lower in eastern populations (yellow and white forms), and pteridines were present only in the red and orange forms, thereby explaining their redder hues. The observed geographical variation in frill carotenoids suggests variation in carotenoid availability across the species' range, which is backed up by the finding that plasma carotenoid concentrations were higher in the red (western) compared to the yellow (eastern) form. Although no correlations were found between individual colour measurements, frill pigments and plasma carotenoids, our results suggest that selective pressures vary across the species' range and we speculate that predation pressures and/or intrasexual signalling context differ between forms.     

Field experiments on a new method for determining age in tsetse flies (Diptera: Glossinidae)

ABSTRACT.

• 1 Data are presented which suggests that the accurate determination of the age of tsetse flies (Glossina morsitans morsitans Westwood and G. pallidipes Austen) in the field can be achieved by measuring the fluorescence content of the head capsule.
• 2 The way in which this can be achieved and further work which would improve the accuracy of the technique are discussed.

     

Isolation and characterization of pteridines from heads of Drosophila melanogaster by a modified thin-layer chromatography procedure

An improved thin-layer chromatography technique is described for the separation of fluorescent compounds found in extracts of heads of Drosophila melanogaster. Eighteen to twenty fluorescent spots are resolved, two of which are xanthurenic acid and 3-hydroxykynurenine, and the remaining spots are presumably pteridines. Of these, nine have been identified and quantitated directly on the chromatograms with a fluorometer. One of the spots present on the chromatogram apparently has not been described previous to this work. Characteristics of this substance, termed quench spot, are presented, several of which indicate that it may be a pteridine or pteridine derivative.T. G. W. is a predoctoral trainee supported by Grant GM 1974 from the National Institute of General Medical Sciences, National Institutes of Health.The Oak Ridge National Laboratory is operated by Union Carbide Corporation for the U.S. Energy Research and Development Administration.     

Partial purification and properties of guanosine triphosphate cyclohydrolase from Drosophila melanogaster

The first enzyme (named GTP cyclohydrolase) in the pathway for the biosynthesis of pteridines has been partially purified from extracts of late pupae and young adults of Drosophila melanogaster. This enzyme catalyzes the hydrolytic removal from GTP of carbon 8 as formate and the synthesis of 2-amino-4-hydroxy-6-(d-erythro-1,2,3-trihydroxypropyl)-7,8-dihydropteridine triphosphate (dihydroneopterin triphosphate). Some of the properties of the enzyme are as follows: it functions optimally at pH 7.8 and at 42 C; activity is unaffected by KCl and NaCl, but divalent cations (Mg²⁺, Mn²⁺, Zn²⁺, and Ca²⁺) are inhibitory; the K _m for GTP is 22 m; and the molecular weight is estimated at 345,000 from gel filtration experiments. Of a number of nucleotides tested, only GDP and dGTP were used to any extent as substrate in place of GTP, and these respective compounds were used only 1.8% and 1.5% as well as GTP.This work was supported by research grants from the National Institutes of Health (AM03442) and the National Science Foundation (GB33929).     

Analysis of pteridines in Pyrrhocoris apterus (L.) (heteroptera,pyrrhocoridae) during development and in body-color mutants

By using thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC), five different pteridines have been quantified in extracts from Pyrrhocoris apterus: neopterin, isoxanthopterin, isoxantholumazine (violapterin), 7-methylxanthopterin, and erythropterin. Biopterin was also detected using HPLC. Pteridines have been analyzed separately in bodies and eyes of the wild type regarding developmental stage and sex. The pteridine content in both bodies and eyes increased from nymphs to 2-day-old adults. After this period, the concentration of pteridines in the eyes of adults remained approximately constant, while in the bodies isoxantholumazine, 7-methylxanthopterin, and isoxanthopterin kept increasing until 20 days. Considering the total amount of pteridines per insect, no qualitative or quantitative differences between males and females have been observed except a lower concentration of erythropterin in female bodies. But when pteridines are analyzed per unit body weight, a lower amount of pteridines is always detected in females due to its bigger size. A new body-color mutant, the yolk body mutant, that goes through developmental colour changes, was also analyzed during development, showing a general deficient accumulation of all pteridines, especially of 7-methylxanthopterin and isoxantholumazine in adult bodies. The effect on pteridine content of three other recessive (white, yellow, mosaic) and two dominant (Pale and Apricot) body-color mutations, has also been studied. A specific pteridine pattern different from the wild type was obtained for each mutant. © 1997 Wiley-Liss, Inc.