cDNA cloning, genomic structure, chromosomal mapping, and functional expression of a novel human alanine aminotransferase
cDNA cloning, genomic structure, chromosomal mapping, and functional expression of a novel human alanine aminotransferase
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DOI：
10.1006/geno.2002.6722
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发表时间：
2002-03-01
期刊：
影响因子：
4.4
通讯作者：
Gong, DW
中科院分区：
文献类型：
--
作者：
Yang, RZ;Blaileanu, G;Gong, DW
丙氨酸氨基转移酶(ALT)催化丙氨酸和2-羟基戊二酸之间的可逆转氨反应，生成丙酮酸和谷氨酸，在葡萄糖和氨基酸的中间代谢中起着关键作用。已知存在两种ALT同工酶，但只有一种ALT基因被克隆，即GPT。在本研究中，我们克隆了GPT的同源基因，并将其命名为GPT2，以及相应的蛋白ALT2。GPT2与先前克隆的GPT在蛋白质水平上有69%的同源性和78%的相似性。人类基因GPT2编码3.9kb的mRNA，由12个外显子组成，跨越基因组约50kb，定位于染色体16q12.1。GPT2和GPT在mRNA表达上的差异在于，GPT2在肌肉、脂肪和肾脏中高表达，而GPT主要在肾脏、肝脏和心脏中表达。此外，GPT2似乎是这些组织中GPT在mRNA水平上的主要形式。在大肠杆菌中表达的ALT2蛋白产生了催化丙氨酸转氨酶的功能重组酶，证实该酶为ALT。GPT2的表达比GPT更丰富，特别是在肌肉和脂肪中，这表明该基因产物在葡萄糖、氨基酸、脂肪酸代谢和动态平衡中具有独特的、以前未被认识的作用。
Alanine aminotransferase (ALT) catalyzes the reversible transamination between alanine and 2-oxoglutarate to form pyruvate and glutamate, and thereby has a key role in the intermediary metabolism of glucose and amino acids. Two ALT isoenzymes are known to exist, but only one ALT gene has been cloned, GPT. In this study, we cloned a homolog of GPT and named it GPT2, and the corresponding protein ALT2. GPT2 shares, 69% identity and 78% similarity at the protein level to the previously cloned GPT. The human gene GPT2 encodes a 3.9-kb mRNA, consists of 12 exons, spanning approximately 50 kb of the genome, and maps to chromosome 16q12.1. GPT2 and GPT differ in mRNA expression in that GPT2 is highly expressed in muscle, fat, and kidney, whereas GPT is mainly expressed in kidney, liver, and heart. In addition, GPT2 seems to be the predominant form of GPT at the mRNA level in these tissues. Expression of ALT2 protein in Escherichia coli produced a functional recombinant enzyme that catalyzes alanine transamination, confirming that the enzyme is an ALT. The more abundant expression of GPT2 than GPT, especially in muscle and fat, suggests a unique and previously unrecognized role of this gene product in glucose, amino acid, and fatty acid metabolism and homeostasis.