テトラヒドロビオプテリンの細胞膜輸送体活性の測定 : アフリカツメガエル卵母細胞による輸送体遺伝子発現系の応用(<特集>ビタミン測定法の現状と課題[IV])

概要

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Supplementation of tetrahydrobiopterin (BH_4), an essential cofactor in nitric oxide and monoamine production, is used in treating a systemic deficiency of BH_4 despite of high cost medication due to short retention of supplied BH_4. Although it also potentially targets a local deficiency such as in some cases of cardiovascular dysfunction, understanding of transport mechanisms underlying the rapid BH_4-excretion is required to improve the therapeutic efficiency. Application of a membrane-protein expression system using Xenopus oocytes followed by a radioisotope assay has widely been employed in transporter research. The assay, however, is made difficult by the labile character of BH_4 while undergoing aerobic oxidation and enzymic conversion. We report here an application of a Xenopus-oocyte expression system to hENT1 and hENT2 for characterization of putative BH_4 transporter. The method allows for the efficient extraction of reduced pterins from a small number of oocytes followed by HPLC and highly sensitive fluorescence detection.
2011-09-25