Brain Protein Synthesis in the Conscious Rat Using L‐[35S]Methionine: Relationship of Methionine Specific Activity Between Plasma and Precursor Compartment and Evaluation of Methionine Metabolic Pathways
Brain Protein Synthesis in the Conscious Rat Using L‐[35S]Methionine: Relationship of Methionine Specific Activity Between Plasma and Precursor Compartment and Evaluation of Methionine Metabolic Pathways
复制标题
使用 L-[35S] 蛋氨酸在清醒大鼠中合成脑蛋白：血浆和前体区室之间蛋氨酸比活性的关系以及蛋氨酸代谢途径的评估
DOI：
--
复制
发表时间：
1992
影响因子：
4.7
通讯作者：
P. Bobillier
中科院分区：
文献类型：
--
作者：
E. Grange;A. Gharib;P. Lepetit;J. Guillaud;N. Sarda;P. Bobillier
摘要：先前开发的用于测量甲硫氨酸掺入脑蛋白速率的方法假设来自蛋白质降解的甲硫氨酸不会再循环进入蛋白质合成的前体池，并且甲硫氨酸通过甲基转移途径的代谢可以忽略不计。为了评价再循环的程度，我们在稳态条件下比较了tRNA结合池中L-[35 S]蛋氨酸的比活性与血浆中的比活性。来自蛋白质降解的甲硫氨酸对前体池的相对贡献为26%。在相同的条件下，甲硫氨酸流入转甲基化循环的相对速率估计为甲硫氨酸掺入脑蛋白速率的10%。这些结果表明：（a）脑中蛋白质降解产生的未标记甲硫氨酸存在显着的再循环;和（B）甲硫氨酸的代谢主要针对蛋白质合成。在正常血浆氨基酸水平下，蛋氨酸是迄今为止在蛋白质合成前体库中稀释度最低的氨基酸。因此，L-[35 S]-甲硫氨酸具有测量体内脑蛋白合成速率所需的放射性生物化学性质，且低估程度最小。
Abstract: The method previously developed for the measurement of rates of methionine incorporation into brain proteins assumed that methionine derived from protein degradation did not recycle into the precursor pool for protein synthesis and that the metabolism of methionine via the transmethylation pathway was negligible. To evaluate the degree of recycling, we have compared, under steady‐state conditions, the specific activity of L‐[35S]methionine in the tRNA‐bound pool to that of plasma. The relative contribution of methionine from protein degradation to the precursor pool was 26%. Under the same conditions, the relative rate of methionine flux into the transmethylation cycle was estimated to be 10% of the rate of methionine incorporation into brain proteins. These results indicate the following: (a) there is significant recycling of unlabeled methionine derived from protein degradation in brain; and (b) the metabolism of methionine is directed mainly towards protein synthesis. At normal plasma amino acid levels, methionine is the amino acid which, to date, presents the lowest degree of dilution in the precursor pool for protein synthesis. L‐[35S]‐Methionine, therefore, presents radiobiochemical properties required to measure, with minimal underestimation, rates of brain protein synthesis in vivo.