CELLULAR AND SUBCELLULAR-LOCALIZATION OF ENZYMES OF ARGININE METABOLISM IN RAT-KIDNEY
CELLULAR AND SUBCELLULAR-LOCALIZATION OF ENZYMES OF ARGININE METABOLISM IN RAT-KIDNEY
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DOI：
10.1042/bj2820369
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发表时间：
1992-03-01
影响因子：
4.1
通讯作者：
BROSNAN, JT
中科院分区：
文献类型：
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作者：
DHANAKOTI, SN;BROSNAN, ME;BROSNAN, JT
大鼠肾脏从谷氨酰胺的肠道代谢中提取瓜氨酸，并将其化学计量转化为精氨酸。这一途径构成了精氨酸的主要内源性来源。我们研究了精氨酸合成酶、精氨酸琥珀酸合成酶和裂解酶，以及分解酶、精氨酸酶和鸟氨酸转氨酶在大鼠肾脏5个区域、皮质小管部分和皮质亚细胞部分的定位。精氨酸琥珀酸合成酶和裂解酶几乎全部存在于皮层。精氨酸酶和鸟氨酸转氨酶主要分布于内皮层和外髓质。由于皮质组织主要由近端弯曲和直小管、远端小管和肾小球组成，我们通过胶原酶消化皮质制备皮质小管碎片，并在Percoll梯度上分离它们。精氨酸琥珀酸合成酶和裂解酶在近曲小管中富集，而精氨酸酶和鸟氨酸转氨酶在近曲小管中富集不到10%。瓜氨酸产生的精氨酸也在近曲小管中富集。肾皮质亚细胞分离显示精氨酸琥珀酸合成酶和裂解酶是胞质性的。因此，我们得出结论，精氨酸合成发生在近曲小管细胞的细胞质中。
Rat kidneys extract citrulline derived from the intestinal metabolism of glutamine and convert it stoichiometrically into arginine. This pathway constitutes the major endogenous source of arginine. We investigated the localization of enzymes of arginine synthesis, argininosuccinate synthase and lyase, and of breakdown, arginase and ornithine aminotransferase, in five regions of rat kidney, in cortical tubule fractions and in subcellular fractions of cortex. Argininosuccinate synthase and lyase were found almost exclusively in cortex. Arginase and ornithine aminotransferase were found in inner cortex and outer medulla. Since cortical tissue primarily consists of proximal convoluted and straight tubules, distal tubules and glomeruli, we prepared cortical tubule fragments by collagenase digestion of cortices and fractionated them on a Percoll gradient. Argininosuccinate synthase and lyase were found to be markedly enriched in proximal convoluted tubules, whereas less than 10% of arginase and ornithine aminotransferase, were recovered in this fraction. Arginine production from citrulline was also enriched in proximal convoluted tubules. Subcellular fractionation of kidney cortex revealed that argininosuccinate synthase and lyase are cytosolic. We therefore conclude that arginine synthesis occurs in the cytoplasm of the cells of the proximal convoluted tubule.