Hepatic glutamate metabolism: a tale of 2 hepatocytes
Hepatic glutamate metabolism: a tale of 2 hepatocytes
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DOI：
10.3945/ajcn.2009.27462z
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发表时间：
2009-09-01
影响因子：
7.1
通讯作者：
Brosnan, John T.
中科院分区：
文献类型：
--
作者：
Brosnan, Margaret E.;Brosnan, John T.
谷氨酸在肝脏氨基酸代谢中起着核心作用，这既因为它在大多数氨基酸的转氨基脱氨作用中所起的作用，也因为精氨酸、鸟氨酸、脯氨酸、组氨酸和谷氨酰胺的分解代谢会产生谷氨酸。现在人们认识到，不同的肝功能局限于不同腺泡区域内的肝细胞亚群。这也是谷氨酸代谢的一个特点。谷氨酰胺的分解代谢和合成在区域上是分开的，谷氨酰胺合成酶局限于肝腺泡3区的一小群肝细胞，而谷氨酰胺酶存在于1区。精氨酸和鸟氨酸的代谢也局限于特定的肝细胞亚群。鸟氨酸氨基转移酶是精氨酸和鸟氨酸分解代谢的调节酶，它与谷氨酰胺合成酶一样局限于3区的细胞，而尿素循环存在于其余的肝细胞中。这种分离有利于这两种不同代谢过程的独立调节。我们只知道肝脏中大约15000个表达基因中很小一部分的腺泡定位。了解代谢过程的腺泡定位对于理解它们与其他肝功能的关系及其调节至关重要。《美国临床营养学杂志》2009年；90（增刊）：857S - 861S
Glutamate plays a central role in hepatic amino acid metabolism, both because of its role in the transdeamination of most amino acids and because the catabolism of arginine, ornithine, proline, histidine, and glutamine gives rise to glutamate. It is now appreciated that different hepatic functions are restricted to hepatocyte subpopulations within different acinar zones. This is also a feature of glutamate metabolism. Glutamine catabolism and synthesis are physically separated by zonation, with glutamine synthetase restricted to a narrow band of hepatocytes in zone 3 of the hepatic acinus, whereas glutaminase occurs in zone 1. Arginine and ornithine metabolism is also restricted to particular hepatocyte subpopulations. Ornithine aminotransferase, the regulated enzyme of arginine and ornithine catabolism, is restricted to the same zone 3 cells as glutamine synthetase, whereas the urea cycle is found in the remaining hepatocytes. This separation facilitates the independent regulation of these 2 different metabolic processes. We know the acinar localization of only a small fraction of the approximate to 15,000 genes expressed in the liver. Knowledge of the acinar localization of metabolic processes is essential for an appreciation of their relation to other hepatic functions and their regulation. Am J Clin Nutr 2009;90(suppl):857S-61S.