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Alanine Transaminase (ALT), also known as alanine aminotransferase (ALAT) or serum glutamic pyruvic transaminase (sGPT), is a homodimeric cytoplasmic pyridoxal phosphate-dependent enzyme involved in cellular nitrogen metabolism, amino acid metabolism, and liver gluconeogenesis.1 ALT mediates conversion of major intermediate metabolites, catalyzing reversible transamination between alanine and α-ketoglutarate to form pyruvate and glutamate.2 ALT is widely distributed in many tissues but is found in greatest abundance in the liver, and to a much lesser extent in the kidneys, heart, and brain.2 The major role of ALT in the liver is the conversion of alanine to glucose which is then exported to the body to be utilized in a multitude of processes. ALT has also been found to play an important role in neuronal function by supplying an important source of neuronal glutamate through the analine-aminotransferase reaction.3 Serum ALT levels are generally low, but may spike during disease states or in the event of tissue injury.4 As such, ALT levels are routinely used as indicators of medical issues, particularly liver diseases. Increased levels can be seen in patients with diabetes, cirrhosis, fatty liver disease, and hepatitis. Beyond liver disease, increased ALT levels have been noted in cases of carcinoma, mononucleosis, muscular dystrophy, and cardiovascular disease.5,6,7,8 Cayman’s Alanine Transaminase Assay Kit provides a convenient method of detecting ALT activity in serum, plasma, tissue samples, and cell lysates. Measurement of the ALT activity is carried out by monitoring the rate of NADH oxidation in a coupled reaction system employing lactate dehydrogenase (LDH). The oxidation of NADH to NAD+ is accompanied by a decrease in absorbance at 340 nm. Under circumstances in which the ALT activity is rate limiting, the rate decrease is directly proportional to the ALT activity in the sample.
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1
Ishiguro, M., Takio, K., Suzuki, M., et al. Complete amino acid sequence of human liver cytosolic alanine aminotransferase (GPT) determined by a combination of conventional and mass spectral methods. Biochemistry 30 10451-10457 (1991).
2
Yang, R., Park, S., Reagan, W.J., et al. Alanine aminotransferase isoenzymes: Molecular cloning and quantitative analysis of tissue expression in rats and serum elevation in liver toxicity. Hepatology 49 598-607 (2009).
3
Erecinska, M., Nelson, D., Nissim, I., et al. Cerebral alanine transport and alanine aminotransferase reaction: Alanine as a source of neuronal glutamate. J Neurochem 62 1953-1964 (1994).
4
Pratt, D.S., Kaplan, M.M. Evaluation of abnormal liver-enzyme results in asymptomatic patients. N Engl J Med 342(17) 1266-1271 (2000).
5
Kim, H.C., Nam, C.M., Jee, S.H., et al. Normal serum aminotransferase concentration and risk of mortality from liver diseases: Prospective cohort study. BMJ (2004).
6
Vozarova, B., Stefan, N., Lindsay, R.S., et al. High alanine aminotransferase is associated with decreased hepatic insulin sensitivity and predicts the development of type 2 diabetes. Diabetes 51 1889-1895 (2002).
7
Prati, D., Taioli, E., Zanella, A., et al. Updated definitions of healthy ranges for serum alanine aminotransferase levels. Ann Intern Med 137 1-9 (2002).
8
Tarao, K., Rino, Y., Ohkawa, S., et al. Association between high serum alanine aminotransferase levels and more rapid development and higher rate of incidence of hepatocellular carcinoma in patients with hepatitis C virus-associated cirrhosis. Cancer 86 589-595 (1999).
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