ENERGETICS OF TRIOSEPHOSPHATE ISOMERASE - FATE OF 1(R)-H-3 LABEL OF TRITIATED DIHYDROXYACETONE PHOSPHATE IN ISOMERASE REACTION
ENERGETICS OF TRIOSEPHOSPHATE ISOMERASE - FATE OF 1(R)-H-3 LABEL OF TRITIATED DIHYDROXYACETONE PHOSPHATE IN ISOMERASE REACTION
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DOI：
10.1021/bi00670a026
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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：
HERLIHY, JM;MAISTER, SG;KNOWLES, JR
研究了磷酸丙糖异构酶催化特异性3 H标记的[1（R）-3H]二羟丙酮磷酸异构化为D-甘油醛3-磷酸的反应。3 H标记在3个可能位点（在[1（R）-3H]二羟基丙酮磷酸中、在D-[2- 3 H]甘油醛3-磷酸中和在溶剂中）中的分布随反应程度而变化。3 H标记从底物磷酸二羟丙酮转移到D-甘油醛3-磷酸的程度在3%和6%之间（取决于反应的程度）。因此，负责从底物中提取质子的酶基与溶剂几乎完全处于同位素平衡。部分反应后剩余底物的比放射性随着反应的进行而增加，表明在交换中间体Quantiquine的阶段，1H底物的优先反应比3 H标记的洗脱更重要，这些结果为前文所述分析的第一步提供了数据。
The isomerization of specifically 3H-labeled [1(R)-3H]dihydroxyacetone phosphate to D-glyceraldehyde 3-phosphate, catalyzed by the enzyme triosephosphate isomerase, was studied. The distribution of the 3H label among the 3 possible sites (in [1(R)-3H]dihydroxyacetone phosphate, in D-[2-3H]glyceraldehyde 3-phosphate, and in the solvent) was followed as a function of the extent of the reaction. The extent of transfer of the 3H label from the substrate dihydroxyacetone phosphate to D-glyceraldehyde 3-phosphate is between 3 and 6% (depending upon the extent of the reaction). The enzymic base responsible for proton abstraction from substrate is, therefore, in almost complete isotopic equilibrium with the solvent. The remaining substrate after partial reaction increases in specific radioactivity as the reaction proceeds, showing that the preferential reaction of 1H substrate is more important than the washing out of 3H label at the stage of the exchanging intermediate Quantitatively, these results provide the data for the 1st step in the analysis described in the previous paper.