Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P17174 (aspartate aminotransferase)
 14,872 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

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.
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PMID:Murine alanine aminotransferase: cDNA cloning, functional expression, and differential gene regulation in mouse fatty liver. 1512 58

In this work, we investigated a potential mechanism behind the observation of increased aminotransferase levels in a phase I clinical trial using a lipid-lowering drug, the peroxisome proliferator-activated receptor (PPAR) alpha agonist, AZD4619. In healthy volunteers treated with AZD4619, serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities were elevated without an increase in other markers for liver injury. These increases in serum aminotransferases have previously been reported in some patients receiving another PPARalpha agonist, fenofibrate. In subsequent in vitro studies, we observed increased expression of ALT1 protein and mRNA in human hepatocytes after treatment with fenofibric acid. The PPAR effect on ALT1 expression was shown to act through a direct transcriptional mechanism involving at least one PPAR response element (PPRE) in the proximal ALT1 promoter, while no effect of fenofibrate and AZD4619 was observed on the ALT2 promoter. Binding of PPARs to the PPRE located at -574 bp from the transcriptional start site was confirmed on both synthetic oligonucleotides and DNA in hepatocytes. These data show that intracellular ALT expression is regulated by PPAR agonists and that this mechanism might contribute to increased ALT activity in serum.
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PMID:PPARalpha regulates the hepatotoxic biomarker alanine aminotransferase (ALT1) gene expression in human hepatocytes. 1845 11