Sawada M, Horikoshi T, Masada M, Akino M, Sugimoto T, Matsuura S, Nagatsu T
Anal Biochem. 1986 Apr;154(1):361-6. doi: 10.1016/0003-2697(86)90537-3.
A highly sensitive and simple assay for the activity of GTP cyclohydrolase I (EC 3.5.4.16) was established using a newly developed radioimmunoassay. D-erythro-7,8-Dihydroneopterin triphosphate formed from GTP by GTP cyclohydrolase I was oxidized by iodine and dephosphorylated by alkaline phosphatase to D-erythro-neopterin, and quantified by a radioimmunoassay for D-erythro-neopterin. This method was highly sensitive and required only 0.2 mg of rat liver tissues for the measurement of the activity. It was reproducible and can be applied for the simultaneous assay of many samples. The activity of GTP cyclohydrolase I was measured in several rat tissues. For example, the enzyme activity in rat striatum (n = 5) was 13.7 +/- 1.5 pmol/mg protein per hour (mean +/- SE), and agreed well with those obtained by high-performance liquid chromatography with fluorescence detection. The activity in the autopsy human brains (caudate nucleus) was measured by this new method for the first time. The activity in the caudate nucleus from parkinsonian patients (n = 6) was 0.82 +/- 0.56 pmol/mg protein per hour which was significantly lower than the control value, 4.22 +/- 0.43 pmol/mg protein per hour (n = 10).
利用新开发的放射免疫分析法建立了一种高灵敏度且简单的鸟苷三磷酸环化水解酶I（EC 3.5.4.16）活性测定方法。由鸟苷三磷酸环化水解酶I作用于GTP生成的D-赤藓糖型-7,8-二氢新蝶呤三磷酸经碘氧化并由碱性磷酸酶去磷酸化生成D-赤藓糖型新蝶呤，然后通过D-赤藓糖型新蝶呤的放射免疫分析法进行定量。该方法灵敏度高，测定活性时仅需0.2mg大鼠肝脏组织。它具有可重复性，可用于同时检测多个样品。在几种大鼠组织中测定了鸟苷三磷酸环化水解酶I的活性。例如，大鼠纹状体（n = 5）中的酶活性为每小时13.7±1.5pmol/mg蛋白质（平均值±标准误），与通过荧光检测的高效液相色谱法获得的结果吻合良好。首次用这种新方法测定了尸检人脑（尾状核）中的活性。帕金森病患者（n = 6）尾状核中的活性为每小时0.82±0.56pmol/mg蛋白质，显著低于对照值每小时4.22±0.43pmol/mg蛋白质（n = 10）。
