Effect of dietary protein on the liver content and subunit composition of the branched-chain alpha-ketoacid dehydrogenase complex.
Effect of dietary protein on the liver content and subunit composition of the branched-chain alpha-ketoacid dehydrogenase complex.
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膳食蛋白质对肝脏含量和支链α-酮酸脱氢酶复合物亚基组成的影响。
DOI：
10.1006/abbi.1994.1063
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发表时间：
1994
影响因子：
3.9
通讯作者：
Harris,RA
中科院分区：
文献类型：
--
作者：
Zhao,Y;Popov,KM;Shimomura,Y;Kedishvili,NY;Jaskiewicz,J;Kuntz,MJ;Kain,J;Zhang,B;Harris,RA
通过定量免疫印迹法测定肝脏支链α-酮酸脱氢酶复合物的两个亚基在极端蛋白质摄入量（50%与0%蛋白质饮食）下的表达水平。日粮蛋白质缺乏对E1α蛋白含量的降低程度大于E2蛋白。在缺乏蛋白质的动物肝脏中，E1α与E2的比值低于1，而在高蛋白饮食的动物肝脏中，E1α与E2的比值高于1。在0%蛋白质饮食中补充5%亮氨酸（而不是5%缬氨酸）与50%蛋白质饮食具有相同的效果。饮食蛋白质的极端也导致了复合物亚基的mRNA表达的不同模式。E1β信息显示了预期的推论，即高蛋白质喂养大鼠的肝脏中E1 β信息比无蛋白质喂养大鼠的肝脏中E1 β信息更大。相反，E2信息不受两个极端的膳食蛋白质的影响，E1α信息在无蛋白质喂养的大鼠的肝脏中比高蛋白质喂养的大鼠更大。因此，复合物亚基的基因表达的协调调节不会响应饮食蛋白质而发生。转录后调节机制很可能决定复合物的量及其亚基的比例。膳食蛋白质缺乏时E1α/E2蛋白比例降低，可能会增加复合物对支链α-酮酸脱氢酶激酶磷酸化介导的抑制作用的敏感性。
Levels of expression of two subunits of the liver branched-chain α-ketoacid dehydrogenase complex in response to extremes of dietary protein intake (50% versus 0% protein diet) were determined by quantitative immunoblotting. Dietary protein deficiency decreased the amount of E1α protein to a greater extent than E2 protein. The ratio of E1α to E2 was below 1 in the liver of animals starved for protein and above 1 in the liver of animals fed the high-protein diet. Supplementation of the 0% protein diet with 5% leucine (but not 5% valine) had the same effect as the 50% protein diet. The extremes of dietary protein also resulted in a divergent pattern of expression of the mRNAs for the subunits of the complex. The E1β message showed the expected corollary of being greater in the liver of the high-protein-fed rats than the no-protein-fed rats. In contrast, the E2 message was not affected by the two extremes of dietary protein and the E1α message was greater in the liver of the no-protein-fed rats than the high-protein-fed rats. Thus, coordinate regulation of gene expression of the subunits of the complex does not occur in response to dietary protein. Post-transcriptional regulatory mechanisms most likely determine the amount of the complex and the ratio of its subunits. The decrease in E1α/E2 protein ratio that occurs in dietary protein deficiency may increase sensitivity of the complex to phosphorylation-mediated inhibition by branched-chain α-ketoacid dehydrogenase kinase.