Shavlovskiĭ G M, Koltun L V, Kashchenko V E
Biokhimiia. 1978 Nov;43(11):2074-81.
The kinetic properties and regulation of activity of GTP-cyclohydrolase, the enzyme of the first step of flavinogenesis in the Pichia guilliermondii yests, partially purified by gel-filtration were studied. It was found that the curve of the dependence of reaction rate on substrate concentration is non-hyperbolic. FAD inhibited the enzyme activity, while riboflavin and FMN had no such effect. In addition to FAD, 5'-AMP, 3',5'-AMP, ADP, ATP, NAD and NADP inhibited the enzyme activity. Under combined action of FAD and AMP on GTP-cyclohydrolase no synergetic or antagonistic effects of the inhibitors on the enzyme activity were observed. The enzyme appreciably lost its sensitivity to FAD and AMP after thermal treatment. The data obtained suggest that GTP-cyclohydrolase from P. guilliermondii is an allosteric enzyme, which is inhibited by the end product of flavinogenesis FAD, as well as by other 5'-AMP-containing nucleotides.
对季也蒙毕赤酵母中黄素生成第一步的酶——GTP-环水解酶经凝胶过滤部分纯化后的动力学性质及活性调控进行了研究。发现反应速率对底物浓度的依赖曲线是非双曲线型的。FAD抑制该酶活性，而核黄素和FMN则无此作用。除FAD外，5'-AMP、3',5'-AMP、ADP、ATP、NAD和NADP也抑制该酶活性。在FAD和AMP对GTP-环水解酶的联合作用下，未观察到抑制剂对酶活性的协同或拮抗作用。热处理后，该酶对FAD和AMP的敏感性明显丧失。所得数据表明，季也蒙毕赤酵母的GTP-环水解酶是一种别构酶，它受到黄素生成终产物FAD以及其他含5'-AMP的核苷酸的抑制。
