Binding of biliverdin, bilirubin, and thyroid hormones to lipocalin-type prostaglandin D synthase
Binding of biliverdin, bilirubin, and thyroid hormones to lipocalin-type prostaglandin D synthase
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DOI：
10.1021/bi990261p
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发表时间：
1999-06-22
期刊：
影响因子：
2.9
通讯作者：
Urade, Y
中科院分区：
文献类型：
--
作者：
Beuckmann, CT;Aoyagi, M;Urade, Y
脂钙素型前列腺素D合成酶是脑脊液中的一种主要蛋白，最初被称为P-trace。在本研究中，我们研究了前列腺素D合成酶对胆汁色素、甲状腺激素、类固醇激素和脂肪酸的结合能力。我们发现重组酶结合胆汁色素和甲状腺激素，导致固有色氨酸荧光猝灭，出现诱导的亲脂配体的圆二色性，以及胆红素和胆绿素的吸收光谱的红移。通过共振镜技术和表面等离子体共振检测也证实了前列腺素D合成酶与亲脂配体的结合。计算出胆红素、胆红素、l -甲状腺素、3,3',5'-三碘- l -甲状腺原氨酸和3,3'，5-三碘- l -甲状腺原氨酸的解离常数分别为33 nM、37 nM、660 nM、820 nM和2.08 μ M。胆绿素和胆红素下；在与前列腺素D合酶结合后，它们的吸收峰分别从375到380 mm和从439到446 nm发生了变化。与酶结合的胆红素在422 nm处具有（-）棉效应，在472 nm处具有（+）棉效应，具有右手性。这些配体还以非竞争性的浓度依赖性方式抑制前列腺素D合成酶的活性，IC50值在3.9 ~ 10.9 μ M之间。附睾视黄酸结合蛋白和β -乳球蛋白是另外两种结合类视黄酸（如前列腺素D合成酶）的脂钙蛋白，它们与胆汁素色素或甲状腺激素没有任何显著的相互作用。这些结果表明，前列腺素D合酶结合小亲脂配体的特异性不同于其他脂钙素。
Lipocalin-type prostaglandin D synthase is a major protein of the cerebrospinal fluid and was originally known as P-trace. We investigated the binding ability of prostaglandin D synthase toward bile pigments, thyroid hormones, steroid hormones, and fatty acids in this present study. We found that the recombinant enzyme binds bile pigments and thyroid hormones, resulting in quenching of the intrinsic tryptophan fluorescence, the appearance of induced circular dichroism of the lipophilic Ligands, and a red shift of the absorption spectra of bilirubin and biliverdin. The binding of prostaglandin D synthase to Lipophilic ligands was also demonstrated by the resonant mirror technique and surface plasmon resonance detection. The dissociation constants were calculated to be 33 nM, 37 nM, 660 nM, 820 nM, and 2.08 mu M for biliverdin, bilirubin, L-thyroxine, 3,3',5'-triiodo-L-thyronine, and 3,3',5-triiodo-L-thyronine, respectively. Biliverdin and bilirubin under;vent a shift in their absorption peaks from 375 to 380 mm and from 439 to 446 nm, respectively, after binding to prostaglandin D synthase. Bilirubin bound to the enzyme showed a bisignate CD spectrum with a (-) Cotton effect at 422 nm and a (+) Cotton effect at 472 nm, indicating a right-handed chirality. The ligands also inhibited prostaglandin D synthase activity noncompetitively in a concentration-dependent manner, with IC50 values between 3.9 and 10.9 mu M Epididymal retinoic acid-binding protein and beta-lactoglobulin, two other lipocalin proteins that bind retinoids such as prostaglandin D synthase, did not show any significant interaction with bile pigments or thyroid hormones. These results show that prostaglandin D synthase binds small lipophilic ligands with a specificity distinct from that of other Lipocalins.