Author: Prof. Dr. med. Peter Altmeyer

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Last updated on: 29.10.2020

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AAT; alpha-1-AT; alpha-1-PI; alpha-1-proteinase inhibitor; AT

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Alpha-1-antitrypsin is the most important proteinase inhibitor in serum (the alpha-1-globulin fraction in serum consists of about 85% of the alpha-1-antitrypsin protein), an acute phase protein belonging to the family of serine protease inhibitors (also called serpins ). Serpins bind enzymes (serine proteases) such as neutrophil elastase, chymotrypsin, trypsin and thrombin. They form irreversible complexes with the respective serine protease and inactivate them.

A deficiency of alpha-1-antitrypsin does not lead to thrombo-embolic events but to severe heaptic and pulmonary changes.

Clinical picture
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Alpha1-antitrypsin is measured in blood serum and is part of the alpha-1-globulins.

Standard value (alpha1-AT concentration in serum): 0.9-1.8g/l

Alpha-1-antitrypsin deficiency: Alpha-1-antitrypsin deficiency (alpha-1-proteinase inhibitor deficiency) is a hereditary disease in which alpha-1-AT is abnormally produced in the liver and therefore cannot be secreted from hepatocytes. It is based on a point mutation in the alpha-1-AT gene. The following variants are distinguished (depending on their electrophoretic mobility):

  • F(almost)
  • M (medium) - medium mobility
  • S (slow) - slow anodic mobility
  • Z mostly cathodically located
  • Rare variants (named after the birthplace of the patient)

S-Alpha1-AT (Glu 264Val), is found in up to 28% of southern Europeans. In homozygous carriers, a reduction of the alpha1-AT concentration of up to 40% occurs.

Z-Alpha1-AT (Glu342Lys), is found in 4% of Northern Europeans. In homozygous carriers, the alpha1-AT concentration is reduced by 85-90%.

Alpha1-AT is also determined in stool. The enzyme serves as a marker for enteral protein loss (see Enteral protein loss syndrome below)

This section has been translated automatically.

Alpha1-antitrypsin was given the name alpha1-proteinase inhibitor (also known as alpha1-PI) after knowledge of its biochemical function. >75 genetic variants of alpha1-antitrypsin are known. Only a few are associated with a clinically relevant alpha1-antitrypsin deficiency. This is important because it can be associated with severe lung and liver disease.

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  1. HA Neumann (2014) The coagulation system. ABW-Wissenschaftsverlag GmbH Berlin S. 101f.


Last updated on: 29.10.2020