Shin-Ichiro Takikawa

Expression analysis of the aldo-keto reductases involved in the novel biosynthetic pathway of tetrahydrobiopterin in human and mouse tissues.

Tetrahydrobiopterin (BH(4)) acts as a cofactor of the aromatic amino-acid hydroxylases, and its deficiency may result in hyperphenylalaninemia (HPA) and decreased production of the neurotransmitters. BH(4) is synthesized by sepiapterin reductase (SPR) from 6-pyruvoyl-tetrahydropterin (PPH(4)). A patient with SPR deficiency shows no HPA; however, an SPR knockout mouse exhibits HPA. We have reported on the SPR-unrelated novel biosynthetic pathway from PPH(4) to BH(4) (salvage pathway II) in which 3alpha-hydroxysteroid dehydrogenase type 2 and aldose reductase work in concert. In this study, we performed the expression analysis of both proteins in humans and wild-type mice. The results of expression analysis indicated that salvage pathway II worked in human liver; however, it did not act in human brain or in mouse liver and brain. For this reason, a patient with SPR deficiency may show progressive neurological deterioration without HPA, and SPR knockout mice may exhibit HPA and abnormal locomotion activity.

Occurrence of biopterin in the wings ofMorpho butterflies

A blue fluorescent compound was isolated fromMorpho butterfly wings. Based on thin layer chromatographic, UV and CD-spectrophotometric and HPLC analyses, the blue fluorescent compound was identified as L-erythro biopterin. Biopterin is a major component of blue fluorescent pteridines in bothM. sulkowskyi andM. adonis. Pterin and isoxanthopterin can also be detected as minor components in these species. This paper is the first to report the presence of biopterin in butterfly wings.

The occurrence of 7-hydroxybiopterin in the scorpion fly,Panorpa japonica

A purple fluorescent compound was isolated from the integument of scorpion flies. Based on paper chromatographic, UV-spectrophotometric, fluoreometric and HPLC analysis, as well as a chemical color test and various degradation tests, the compound was identified as 7-hydroxybiopterin.

Relationship between Seasonal Colour Dimorphism and Pteridines in the Scorpion Fly, Panorpa japonica, Thunberg

The combination of the morphological and biochemical approaches shows that sepiapterin is characteristically located at the pigment granules in the integument of the insect. We report here that the contents of various pteridines and the activities of related enzymes (GTP-cyclohydrolase I, 6-pyruvoyl-tetrahydropterin synthase and sepiapterin reductase) were measured at several stages after emergence of both yellow type fly and black one.

Characterization of a dihydropterin deaminase from Drosophila melanogaster

Abstract A highly specific dihydropterin deaminase was discovered in Drosophila melanogaster and was purified 60-fold over that of the crude extract. The enzyme specifically deaminates 7,8-dihydropterin forming the corresponding 7,8-dihydrolumazine. The enzyme does not deaminate the following compounds: pterin, xanthopterin, dihydroxanthopterin, sepiapterin, isosepiapterin, biopterin, dihydrobiopterin, neopterin, 6-hydroxymethylpterin, 6-methylpterin, 7-methylpterin, 6,7-dimethylpterin, pterin-6-carboxylic acid, isoxanthopterin, isoxanthopterin-6-carboxylic acid, 6-methylisoxanthopterin, 6-methyl-tetrahydropterin, drosopterin and isodrosopterin. The pH optimum of the enzymatic reaction is approximately 8.5 and the K m value is 1.3 mM. The molecular weight of the enzyme is 73,000 as estimated by gel filtration. The non-fluorescent product of the reaction, 7,8-dihydrolumazine, was non-enzymatically oxidized to blue fluorescent 6-hydroxylumazine.