BIOSYNTHESIS OF CATECHOLAMINES

我们实验室以前的研究表明，四氢生物蝶呤 (BH4)在体外激活正弦羟化酶磷酸酶。本 结果与这些早期的发现一致，并表明BH 4具有 在完整的大鼠纹状体突触体中也有类似的作用。增加 突触体内BH4，由摄入外源性蝶呤引起，产生 酪氨酸羟化酶的去磷酸化增加， 突触体该作用是快速的和浓度依赖性的。此外，委员会认为， 该反应似乎对BH4具有特异性。一个类似的和可逆的 用BH 4前体Sepiapterin观察到效果，而生物蝶呤 几乎没有活动。未来的研究将继续解决这一小说 监管职能，以进一步表征的模式， BH_4的作用及其在体内的生物学意义。 其他研究使用大鼠纹状体切片来检查酪氨酸的作用 羟化酶在高苯丙氨酸血症状态的大脑。具体地说， 内源性酪氨酸对蛋白结合酪氨酸的相对贡献 由外源3H-苯丙氨酸形成的3H-酪氨酸与由外源3H-苯丙氨酸形成的3H-酪氨酸相比， 来自外源性14 C-酪氨酸。新形成的3H-酪氨酸掺入 蛋白质被证明。这种3 H-酪氨酸掺入依赖于 外源性3H-苯丙氨酸的浓度。

Previous studies in our laboratory have shown that tetrahydrobiopterin (BH4) activates a sine hydroxylase phosphatase in vitro. The present results,are consistent with these earlier findings and suggest that BH4 has a similar effect in intact rat striatal synaptosomes. An increase in intrasynaptosomal BH4, caused by the intake of exogenous pterin, produced an increase in the dephosphorylation of tyrosine hydroxylase in intact synaptosomes. The effect was rapid and concentration dependent. Moreover, the response appeared to be specific for BH4. A similar and reversible effect was observed with the BH4 precursor sepiapterin, whereas biopterin was virtually inactive. Future studies will continue to address this novel regulatory function with a view to characterizing further the mode of action of BH4 and its biological significance in vivo. Other studies have used rat striatal slices to examine the role of tyrosine hydroxylase in the brain during hyperphenylalanemic states. Specifically, the relative contribution to the protein-bound tyrosine of endogenously formed 3H-tyrosine from exogenous 3H-phenylalanine was compared to that from exogenous l4C-tyrosine. Newly formed 3H-tyrosine incorporation into protein was demonstrated. This 3H-tyrosine incorporation was dependent on the concentration of exogenous 3H-phenylalanine.