What are Liver Enzymes?

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  • Written By: Helga George
  • Edited By: Allegra J. Lingo
  • Last Modified Date: 17 August 2019
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Liver enzymes are proteins located in the liver that speed up the rate of reactions to make them chemically feasible. The liver is the primary area of detoxification in the body and metabolizes many drugs and compounds that enter the body’s system. It is also the source of much of the stored glucose for energy. A liver enzyme breaks down complex glucose polymers into individual units of glucose that are released into the blood to be utilized by the body. The degree of liver function is measured by the assay of liver enzymes known as transaminases.

Much of the detoxification of chemicals is mediated by liver enzymes. The liver has a number of different cytochrome P450 enzymes that carry out drug metabolism. This is generally beneficial, but in some cases the degradation of one prescription drug can cause side effects with another. Many of these P450s are capable of degrading a wide variety of foreign compounds, such as toxic chemicals, that are known as xenobiotics. Humans are thought to have evolved a great variety of detoxifying P450s from being exposed to the large number of secondary metabolites in plants that have been consumed over the course of evolution.


The liver is also a major storage organ for reserve sugar stores. Sugar is stored as glycogen, a long, branching polymer of glucose units that is stored as granules. When energy levels in the body are low, the enzyme glycogen phosphorylase releases individual glucose molecules from the glycogen. A complex regulatory system of liver enzymes is involved in this process, which results in glucose entering the blood stream to be utilized by other organs.

Liver function is measured clinically by checking for the presence of elevated liver enzymes known as transaminases. There are a number of transaminases present in the body, but two in particular are measured. These are aspartate transaminase (AST) and alanine transaminase (ALT).

Both liver enzymes can be affected by a variety of liver conditions. If the liver has been damaged, each will have leaked into the bloodstream. Thus, a simple blood test can diagnose liver damage. ALT is generally examined more closely to detect damage to the liver. An examination of AST can be helpful at determining if the damage is due to abuse of alcohol.

Although the liver does not produce digestive enzymes, it does produce bile. This is a compound that reacts with lipids. Bile helps break them into little pieces so they can be digested more easily. The digestive compound from the liver is stored in the gallbladder and exerts its effects in the duodenum.


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