BIOSYNTHESIS OF CATECHOLAMINES

研究了酪氨酸羟化酶的几个基本性质， 这个实验室。 酪氨酸羟化酶纯化至表观均一 从大鼠嗜铬细胞瘤细胞，和许多生物化学和物理 这种肿瘤酶的性质进行了表征。 此外，老鼠 克隆了嗜铬细胞瘤酪氨酸羟化酶基因，并在E.杆菌和 随后纯化至均质。 纯重组酶 表现出天然活化酪氨酸的许多动力学性质， 羟化酶 这一激活的性质目前正在 调查 其他研究探讨了酪氨酸羟化酶的机制 磷酸化和去磷酸化的完整大鼠纹状体突触体。 早期的证据揭示了酪氨酸的去磷酸化途径 羟化酶，显着刺激四氢生物蝶呤原位。 四氢生物蝶呤的这种作用被证明是特异性的， 浓度依赖性。 此外，观察到以下效果： 突触体与cAMP孵育，但不与钙离子载体或高钙离子载体孵育 钾，并消除了对四氢生物蝶呤的反应， 冈田酸 这些发现表明， 四氢生物蝶呤由2A型蛋白磷酸酶介导， 针对c-AMP依赖性蛋白磷酸化位点 激酶。 目前的研究正试图确定具体的 四氢生物嘌呤的磷酸氨基酸靶位点。

Several essential properties of tyrosine hydroxylase were investigated in this laboratory. Tyrosine hydroxylase was purified to apparent homogeneity from rat pheochromocytoma cells, and many of the biochemical and physical properties of this tumor enzyme were characterized. In addition, rat pheochromocytoma tyrosine hydroxylase was cloned, expressed in E. coli, and subsequently purified to homogeneity. The pure recombinant enzyme exhibited many of the kinetic properties of native, activated tyrosine hydroxylase. The nature of this activation is currently under investigation. Other studies explored the mechanisms of tyrosine hydroxylase phosphorylation and dephosphorylation in intact rat striatal synaptosomes. Earlier evidence unveiled a pathway of dephosphorylation for tyrosine hydroxylase which was markedly stimulated by tetrahydrobiopterin in situ. This effect of tetrahydrobiopterin was shown to be specific and concentration dependent. Furthermore, the effect was observed following incubation of synaptosomes with cAMP, but not calcium ionophores or high potassium, and the response to tetrahydrobiopterin was eliminated by okadaic acid. These findings suggest that the action of tetrahydrobiopterin is mediated by a protein phosphatase of type 2A and is directed at sites that are phosphorylated by c-AMP-dependent protein kinase. Current studies are attempting to identify the specific phosphoamino acid target sites for tetrahydrobioptern.