ENERGETICS OF TRIOSEPHOSPHATE ISOMERASE - APPEARANCE OF SOLVENT TRITIUM IN SUBSTRATE DIHYDROXYACETONE PHOSPHATE AND IN PRODUCT
ENERGETICS OF TRIOSEPHOSPHATE ISOMERASE - APPEARANCE OF SOLVENT TRITIUM IN SUBSTRATE DIHYDROXYACETONE PHOSPHATE AND IN PRODUCT
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DOI：
10.1021/bi00670a027
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发表时间：
1976-01-01
期刊：
影响因子：
2.9
通讯作者：
KNOWLES, JR
中科院分区：
文献类型：
--
作者：
MAISTER, SG;PETT, CP;KNOWLES, JR
当磷酸丙糖异构酶在3H2O中催化磷酸二羟丙酮异构化为D-甘油醛3-磷酸时，底物和产物都被标记。产物的比放射性约为溶剂的80%，这表明在C-2处的包被中间体的质子化（形成酶结合产物D-甘油醛3-磷酸）之后是不涉及H+转移的较慢步骤。部分反应后剩余底物的比放射性随反应进行而升高，表明与介质交换H+的反应中间体返回磷酸二羟丙酮（吸收3H）的频率约为其转化为D-甘油醛3-磷酸的1/3。这些结果允许在催化反应中的能量势垒的相对高度的定性描述，并有助于该过程的能量学的定量分析。
When the isomerization of dihydroxyacetone phosphate to D-glyceraldehyde 3-phosphate is catalyzed by triosephosphate isomerase in 3H2O, both the substrate and product become labeled. The specific radioactivity of the product is about 80% that of the solvent, which shows that the protonation of the enediol intermediate at C-2 (to form the enzyme-bound product D-glyceraldehyde 3-phosphate) is followed by a slower step not involving H+ transfer. The specific radioactivity of the remaining substrate after partial reaction rises as the reaction proceeds and shows that the reaction intermediate that exchanges H+ with the medium returns to dihydroxyacetone phosphate (picking up 3H) about 1/3 as often as it is coverted to D-glyceraldehyde 3-phosphate. These results allow a qualitative description of the relative heights of the energy barriers in the catalyzed reaction and contribute to the quantitative analysis of the energetics of the process.