Brosnan M E, Lowry A, Wasi Y, Lowry M, Brosnan J T
Can J Physiol Pharmacol. 1985 Oct;63(10):1234-8. doi: 10.1139/y85-204.
Branched-chain-amino-acid:alpha-ketoglutarate transaminase and branched-chain alpha-ketoacid dehydrogenase have been assayed in brains of control and of streptozotocin-induced diabetic rats. Enzyme activities were measured in five distinct regions of the brain: cerebellum, pons + medulla, midbrain, thalamus + hypothalamus, and telencephalon. Subcellular distribution of these enzymes in whole brain was assessed by fractionating brain homogenate into cytoplasm, free mitochondria, and synaptosomes. The following enzymes were used as markers: lactate dehydrogenase for cytoplasm, glutamate dehydrogenase for mitochondria, and glutamate decarboxylase for synaptosomes. The activity of the branched-chain amino acid transaminase in all brain regions was considerably higher than that of the branched-chain alpha-ketoacid dehydrogenase. While the highest activity of the transaminase occurred in brain-stem regions, the highest activity of the dehydrogenase was present in cerebellum and telencephalon. Diabetes did not affect the activity of the transaminase, but it caused a decrease in the total activity of the dehydrogenase in midbrain and in thalamus + hypothalamus. The transaminase was localized in the cytoplasmic fraction of whole brain, while the dehydrogenase was enriched in the free mitochondria.
α-酮戊二酸转氨酶和支链α-酮酸脱氢酶进行了测定。在大脑的五个不同区域测量了酶活性：小脑、脑桥+延髓、中脑、丘脑+下丘脑和端脑。通过将脑匀浆分离为细胞质、游离线粒体和突触体来评估这些酶在全脑中的亚细胞分布。使用以下酶作为标志物：乳酸脱氢酶用于细胞质，谷氨酸脱氢酶用于线粒体，谷氨酸脱羧酶用于突触体。所有脑区中支链氨基酸转氨酶的活性均显著高于支链α-酮酸脱氢酶的活性。转氨酶的最高活性出现在脑干区域，而脱氢酶的最高活性则存在于小脑和端脑中。糖尿病不影响转氨酶的活性，但会导致中脑以及丘脑+下丘脑中脱氢酶的总活性降低。转氨酶定位于全脑的细胞质部分，而脱氢酶则在游离线粒体中富集。
