Karobath M
Proc Natl Acad Sci U S A. 1971 Oct;68(10):2370-3. doi: 10.1073/pnas.68.10.2370.
Tyrosine hydroxylase activity of synaptosomes isolated from rat brain was examined. A modified tritium-displacement assay was used, which allowed the measurement of tyrosine hydroxylase activity without the addition of either inhibitors of the metabolism of the hydroxylated products or added exogenous cofactor. The enzyme activity was strongly inhibited by the addition of exogenous catecholamines and 3,4-dihydroxy-L-phenyl-alanine. Aromatic amines other than catechols did not markedly influence tyrosine hydroxylase activity. These in vitro findings support the hypothesis that synthesis of catecholamines is regulated by a mechanism of end-product inhibition at the tyrosine hydroxylase step.
对从大鼠大脑分离出的突触体的酪氨酸羟化酶活性进行了检测。采用了一种改良的氚置换测定法，该方法无需添加羟基化产物代谢抑制剂或添加外源性辅因子就能测量酪氨酸羟化酶活性。添加外源性儿茶酚胺和3,4-二羟基-L-苯丙氨酸会强烈抑制该酶的活性。除儿茶酚外的芳香胺对酪氨酸羟化酶活性没有明显影响。这些体外研究结果支持了这样一种假说，即儿茶酚胺的合成在酪氨酸羟化酶步骤受终产物抑制机制的调节。
