Murine alanine aminotransferase: cDNA cloning, functional expression, and differential gene regulation in mouse fatty liver
Murine alanine aminotransferase: cDNA cloning, functional expression, and differential gene regulation in mouse fatty liver
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DOI：
10.1002/hep.20182
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发表时间：
2004-05-01
期刊：
影响因子：
13.5
通讯作者：
Gong, DW
中科院分区：
文献类型：
--
作者：
Jadaho, SB;Yang, RZ;Gong, DW
丙氨酸氨基转移酶（ALT）是临床上广泛使用的肝脏完整性或肝细胞损伤的指标，也是中间代谢的关键酶。在这项研究中，我们克隆了互补的DNA的小鼠同源的人丙氨酸氨基转移酶1和2（ALT 1和ALT 2）。小鼠ALT 1（mALT 1）和ALT 2（mALT 2）的推导肽在氨基酸水平上分别与它们的人对应物共享87%和93%的同一性。小鼠ALT基因定位于不同的染色体，mALT 1基因（gpt 1）位于15号染色体，mALT 2基因（gpt 2）位于8号染色体。鼠gpt 1和gpt 2的信使RNA表达不同：gpt 1主要在肝脏、肠和白色脂肪组织中表达，gpt 2在肌肉、肝脏和白色脂肪组织中高度表达。重组mALT 1和mALT 2蛋白在大肠杆菌中的表达。大肠杆菌）产生催化丙氨酸转氨作用的功能酶。在肥胖动物模型中评价了ALT同工酶在肝病中的潜在诊断价值。在肥胖小鼠的脂肪肝中，ALT 2基因表达被诱导2倍，但ALT 1保持不变。此外，在脂肪肝中，总肝脏ALT活性显著升高30%，而天冬氨酸转氨酶（AST）活性保持不变。总之，这些结果表明，ALT 2可能是负责肝脂肪变性的ALT活性增加，并提供证据表明，ALT同工酶特异性测定可能比目前临床使用的总ALT活性测定具有更高的诊断价值。
Alanine aminotransferase (ALT) is a widely used index of liver integrity or hepatocellular damage in clinics as well as a key enzyme in intermediatary metabolism. In this study, we have cloned the complementary DNAs of murine homologues of human alanine aminotransferase 1 and 2 (ALT1 and ALT2). The deduced peptides of murine ALT1 (mALT1) and ALT2 (mALT2) share 87% and 93% identity, respectively, with their human counterparts at the amino acid level. Murine ALT genes localize to separate chromosomes, with mALT1 gene (gpt1) on chromosome 15 and mALT2 gene (gpt2) on chromosome 8. The murine gpt1 and gpt2 differ in messenger RNA expression: gpt1 is mainly expressed in liver, bowel, and white adipose tissue and gpt2 is highly expressed in muscle, liver, and white adipose tissue. Expression of recombinant mALT1 and mALT2 proteins in Escherichia coli (E. coli) produced functional enzymes that catalyze alanine transamination. The potential diagnostic value of ALT isoenzymes in liver disease was evaluated in an obese animal model. In fatty livers of obese mice, ALT2 gene expression is induced 2-fold, but ALT1 remains the same. Furthermore, in fatty liver, total hepatic ALT activity is elevated significantly by 30% whereas aspartate aminotransferase (AST) activity remains unchanged. In conclusion, these results indicate that ALT2 may be responsible for the increased ALT activity in hepatic steatosis and provide evidence that an ALT isoenzyme-specific assay may have more diagnostic value than the total ALT activity assay currently in clinical use.