p-ethynylphenylalanine:: A potent inhibitor of tryptophan hydroxylase
p-ethynylphenylalanine:: A potent inhibitor of tryptophan hydroxylase
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DOI：
10.1046/j.1471-4159.2000.0742067.x
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发表时间：
2000-05-01
影响因子：
4.7
通讯作者：
Vrana, KE
中科院分区：
文献类型：
--
作者：
Stokes, AH;Xu, YM;Vrana, KE
色氨酸羟化酶（TPH）是血清素生物合成的起始酶和限速酶。酶活性取决于分子氧、四氢蝶呤共底物和二价铁。本研究表明，TPH 受到一种新化合物对乙炔基苯丙氨酸 (pEPA) 的抑制，该化合物是由三甲基甲硅烷基乙炔与 N-叔丁氧羰基-4-碘-L-苯丙氨酸甲酯发生 Heck 反应产生的。 pEPA 是比对氯苯丙氨酸 (pCPA) 更有效、更特异的 TPH 抑制剂。在本研究中，pEPA 被证明能够在体外竞争性且可逆地抑制 TPH（相对于色氨酸，K-i = 32.6 +/- 6.2 mu M）。 pEPA 对酪氨酸羟化酶 (EC 1.14.16.2)（儿茶酚胺生物合成的起始酶和限速酶）几乎没有抑制活性，并且对苯丙氨酸羟化酶或酪氨酸酶没有抑制作用。此外，pEPA 是血清素转运蛋白和几种血清素受体的不良配体。给大鼠注射 pEPA (30 mg/kg)，注射后 24 小时，大脑匀浆中的 TPH 活性降低 95 +/- 5%，同时血清素和 5-羟基吲哚-3-乙酸水平 (85%) 降低。相比之下，pCPA 仅在 10 倍浓度（300 mg/kg）时产生类似的效果（TPH 活性降低 87 +/- 5%）。这些结果表明，pEPA 在体外和体内都是一种选择性、可逆且有效的 TPH 抑制剂。 pEPA 选择性和可逆性抑制血清素生物合成的潜力可能有助于表征血清素在行为和生理活动中的作用。
Tryptophan hydroxylase (TPH) is the initial and rate-limiting enzyme in serotonin biosynthesis. The enzyme activity is dependent on molecular oxygen, a tetrahydropterin cosubstrate, and ferrous iron. The present study demonstrates that TPH is inhibited by a novel compound, p-ethynylphenylalanine (pEPA), produced by the Heck reaction of trimethylsilylacetylene with N-tert-butyloxycarbonyl-4-iodo-L-phenylalanine methyl ester. pEPA is a more potent and specific inhibitor of TPH than p-chlorophenylalanine (pCPA). In the present study, pEPA was demonstrated to inhibit competitively and reversibly TPH in vitro (K-i = 32.6 +/- 6.2 mu M vs. tryptophan). pEPA displayed little inhibitory activity toward tyrosine hydroxylase (EC 1.14.16.2), the initial and rate-limiting enzyme for catecholamine biosynthesis, and no inhibition of phenylalanine hydroxylase or tyrosinase. In addition, pEPA was a poor ligand for the serotonin transporter and several serotonin receptors. Administration of pEPA (30 mg/kg) to rats produced a 95 +/- 5% decrease in TPH activity in brain homogenates and a concomitant decrease in serotonin and 5-hydroxyindole-3-acetic acid levels (85%) at 24 h after injection. In contrast, pCPA produced a similar effect (87 +/- 5% decrease in TPH activity) only at 10 times the concentration (300 mg/kg). These results suggest that pEPA is a selective, reversible, and potent inhibitor of TPH both in vitro and in vivo. The potential for pEPA to inhibit selectively and reversibly the biosynthesis of serotonin may contribute to the characterization of the role of serotonin in behavioral and physiological activities.