大鼠离体肌肉、神经和主动脉中支链氨基酸氧化的调节

Regulation of branched-chain amino acid oxidation in isolated muscles, nerves and aortas of rats.

作者信息

Buse M G, Jursinic S, Reid S S

出版信息

Biochem J. 1975 Jun;148(3):363-74. doi: 10.1042/bj1480363.

DOI:10.1042/bj1480363

PMID:1200982

原文链接:https://pmc.ncbi.nlm.nih.gov/articles/PMC1165553/

Abstract

The oxidation of the three branched-chain amino acids was regulated in parallel fashion in rat tissues studied in vitro. 2. With 0.1 mM-[1-14C]isoleucine as substrate in the presence of 5.5 mM-glucose, 14CO2 production was 0.6 mumol/2 h per g in the aorta, 0.3 in peripheral nerve, 0.2 in muscle and 0.13 in spinal cord. 3. The ratio 14C oxidized/14C incorporated into proteins with 0.1 mM-[1-14C]leucine was 1.3 in hemidiaphragms, 3.3 in sciatic nerve and 1.0 in nerves undergoing Wallerian degeneration. Leucine oxidation decreased only slightly during degeneration, but protein synthesis doubled. 4. Hemidiaphragms incubated with [1-14C]leucine or 4-methyl-2-oxo[1-14C]pentanoate increased 14CO2 production 7-9-fold as substrate concentration was increased from 0.1 to 0.5 mM; under the same conditions 14CO2 production by nerves increased only 2-3-fold. 5. 2-Oxoglutarate stimulated the oxidation of the branched-chain amino acids by muscles and peripheral nerves and the oxidation of 4-methyl-2-oxopentanoate by hemidiaphragms but not by nerves. 6. Octanoate (0.1-1.0 mM) markedly stimulated the oxidation of branched-chain amino acids and of 4-methyl-2-oxopentanoate in hemidiaphragms, but inhibited oxidation of both by peripheral nerves and spinal cord. In aortas, oxidation of isoleucine (the only substance tested) was inhibited by octanoate. 7. The effects of octanoate and 2-oxoglutarate on leucine oxidation by hemidiaphragms were additive at low concentrations. When maximally stimulating concentrations of either agent were used, addition of the other was ineffective. 8. Pyruvate inhibited the oxidation of branched-chain amino acids and 4-methyl-2-oxopentanoate in all tissues tested. 9. Insulin did not affect the oxidation of 4-methyl-2-oxopentanoate by muscles or nerves. 10. The oxidative decarboxylation of the branched-chain alpha-oxo acids is suggested as a regulatory site of branched-chain amino acid oxidation. Differences in regulation between muscle on the one hand, and nerve and aorta on the other, are discussed.

摘要

在体外研究的大鼠组织中，三种支链氨基酸的氧化以平行方式受到调节。2. 以0.1 mM - [1 - 14C]异亮氨酸为底物，在5.5 mM葡萄糖存在的情况下，每克主动脉中14CO2的生成量为0.6 μmol/2小时，外周神经中为0.3，肌肉中为0.2，脊髓中为0.13。3. 用0.1 mM - [1 - 14C]亮氨酸时，半膈肌中14C氧化/14C掺入蛋白质的比率为1.3，坐骨神经中为3.3，发生华勒氏变性的神经中为1.0。在变性过程中亮氨酸氧化仅略有下降，但蛋白质合成增加了一倍。4. 用[1 - 14C]亮氨酸或4 - 甲基 - 2 - 氧代[1 - 14C]戊酸酯孵育半膈肌时，随着底物浓度从0.1 mM增加到0.5 mM，14CO2生成量增加7 - 9倍；在相同条件下，神经中14CO2生成量仅增加2 - 3倍。5. 2 - 氧代戊二酸刺激肌肉和外周神经中支链氨基酸的氧化以及半膈肌中4 - 甲基 - 2 - 氧代戊酸酯的氧化，但不刺激神经中的氧化。6. 辛酸（0.1 - 1.0 mM）显著刺激半膈肌中支链氨基酸和4 - 甲基 - 2 - 氧代戊酸酯的氧化，但抑制外周神经和脊髓中两者的氧化。在主动脉中，辛酸抑制异亮氨酸（唯一测试的物质）的氧化。7. 辛酸和2 - 氧代戊二酸对半膈肌亮氨酸氧化的影响在低浓度时是相加的。当使用任何一种试剂的最大刺激浓度时，添加另一种试剂无效。8. 丙酮酸抑制所有测试组织中支链氨基酸和4 - 甲基 - 2 - 氧代戊酸酯的氧化。9. 胰岛素不影响肌肉或神经中4 - 甲基 - 2 - 氧代戊酸酯的氧化。10. 支链α - 氧代酸的氧化脱羧被认为是支链氨基酸氧化的一个调节位点。讨论了肌肉与神经和主动脉之间调节的差异。