Studies on enzymes concerned with the reductive metabolism of carotenoids in fish

• Project/Area Number: 16K14982
• Research Category: Grant-in-Aid for Challenging Exploratory Research
• Allocation Type: Multi-year Fund
• Research Field: Aquatic life science
• Research Institution: The University of Tokyo
• Principal Investigator: Okada Shigeru 東京大学, 大学院農学生命科学研究科(農学部), 准教授 (00224014)
• Project Period (FY): 2016-04-01 – 2019-03-31
• Project Status: Completed (Fiscal Year 2018)
• Budget Amount: ¥3,770,000 (Direct Cost: ¥2,900,000、Indirect Cost: ¥870,000); Fiscal Year 2017: ¥1,560,000 (Direct Cost: ¥1,200,000、Indirect Cost: ¥360,000); Fiscal Year 2016: ¥2,210,000 (Direct Cost: ¥1,700,000、Indirect Cost: ¥510,000)
• Keywords: カロテノイド / 魚類 / 代謝 / 酵素 / 還元 / 酸化

Outline of Final Research Achievements

Several species of fish have a reductive pathway of carotenoids in which astaxanthin is converted into zeaxanthin or lutein. In this study, identification of enzymes concerned with the reductive metabolism of carotenoids in fish was tried. In order to obtain some information on substrate specificity of the enzyme that converts astaxanthin into zeaxanthin or lutein, medaka (Oryzias latipes) was fed with either of three stereoisomers of astaxanthin. As fishes fed with any stereoisomer of astaxanthin could accumulate more zeaxanthin and lutein than the control fish, it was suggested that the enzyme concerned with reductive conversion of astaxanthin does not distinguish stereoisomers of astaxanthin and can use them as its substrate.

Academic Significance and Societal Importance of the Research Achievements

本研究により、魚類に存在するアスタキサンチンの還元的代謝に関与する酵素の一部特性を知ることができた。この成果を基に、当該酵素が特定されれば、その反応メカニズムを解析することで、魚類におけるカロテノイド代謝を分子レベルで解明することが可能となり、魚類生化学、生理学への貢献度は非常に大きいものがあると考えられる。さらに、カロテノイドの還元的代謝経路を活性化させた魚を作り出すことができれば、餌にビタミンAの添加をしなくても健全な生育が可能な、ビタミンA要求性の低い新規養殖魚の作出も可能になる。