Alanine transaminase
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Alanine transaminase or ALT is (mostly) a liver enzyme (EC 2.6.1.2 (http://us.expasy.org/cgi-bin/nicezyme.pl?2.6.1.2)). It is also called serum glutamate pyruvate transaminase (SGPT) or alanine aminotransferrase (ALAT). This enzyme is release into the plasma by liver cell death, a normal event. However, when liver cell death increases, ALT levels rise above the normal range. The spillover of this enzyme into blood is routinely measured as a marker of abnormal liver-cell damage. For example, alcoholic or viral hepatitis will increase ALT levels, as will severe congestive heart failure. An elevated ALT in the presence of normal levels of plasma alkaline phosphatase helps distinguish liver disease caused by liver-cell damage from diseases caused by problems in biliary ducts.
ALT is markedly raised in hepatitis and other acute liver damage. The enzyme aspartate transaminase (AST) has a similar role, but this enzyme tends to be found in other tissues, such as the heart, so is not as specific to the liver.