人类和大鼠肝脏中的α-酮异己酸分解代谢
The alpha-ketoisocaproate catabolism in human and rat livers.
作者信息
Xu M, Nakai N, Ishigure K, Nonami T, Nagasaki M, Obayashi M, Li Z, Sato Y, Fujitsuka N, Murakami T, Shimomura Y
机构信息
Department of Sports Medicine, Nagoya University, Nagoya, 464-8601, Japan.
出版信息
Biochem Biophys Res Commun. 2000 Oct 5;276(3):1080-4. doi: 10.1006/bbrc.2000.3566.
Catabolism of alpha-ketoisocaproate in liver is mediated by cytosolic alpha-ketoisocaproate dioxygenase (KICD) and mitochondrial branched-chain alpha-keto acid dehydrogenase complex (BCKDC). The latter is believed to be involved in the main pathway of the KIC catabolism. In the present study, we measured the activities of KICD and BCKDC in human and rat livers. The KICD activity in human liver was 0.9 mU/g tissue, which was 14.2% of the total activity of BCKDC, and that in rat liver was 4.2 mU/g tissue, which was only 1.0% of the total activity, suggesting that KICD in human liver plays a relatively important role in the alpha-ketoisocaproate catabolism. The KICD activity in human liver was significantly increased by cirrhosis. In rat liver, the enzyme activity was markedly increased by physical training and streptozotocin-induced diabetes, but not by feeding of a diet rich in branched-chain amino acids, although BCKDC activity was increased by feeding of the diet.
肝脏中α-酮异己酸的分解代谢由胞质α-酮异己酸双加氧酶（KICD）和线粒体支链α-酮酸脱氢酶复合体（BCKDC）介导。后者被认为参与了KIC分解代谢的主要途径。在本研究中，我们测定了人和大鼠肝脏中KICD和BCKDC的活性。人肝脏中的KICD活性为0.9 mU/g组织，占BCKDC总活性的14.2%，而大鼠肝脏中的KICD活性为4.2 mU/g组织，仅占总活性的1.0%，这表明人肝脏中的KICD在α-酮异己酸分解代谢中发挥相对重要的作用。肝硬化会显著增加人肝脏中的KICD活性。在大鼠肝脏中，体育锻炼和链脲佐菌素诱导的糖尿病会使该酶活性显著增加，但富含支链氨基酸的饮食喂养不会使其增加，尽管这种饮食喂养会增加BCKDC的活性。
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