Mutation of antitrypsin to antithrombin. alpha 1-antitrypsin Pittsburgh (358 Met leads to Arg), a fatal bleeding disorder

N Engl J Med. 1983 Sep 22;309(12):694-8. doi: 10.1056/NEJM198309223091203.


Our previous studies predicted a functional relationship between the plasma proteins alpha 1-antitrypsin and antithrombin III. To elucidate this relationship we investigated the plasma of a 14-year-old boy who had died from an episodic bleeding disorder. A variant alpha 1-antitrypsin was identified in which the methionine at position 358 had been replaced by an arginine. This had converted the alpha 1-antitrypsin from its normal function as an inhibitor of elastase to that of an inhibitor of thrombin. This finding indicates that the reactive center of alpha 1-antitrypsin is methionine 358, which acts as a bait for elastase, just as the normal reactive center of antithrombin III is arginine 393, which acts as a bait for thrombin. The independence of the new thrombin inhibitor from heparin control explains the bleeding disorder; it also indicates that heparin normally acts directly on antithrombin III, revealing its inherent inhibitory activity. The episodic nature of the bleeding was a consequence of the mutant protein's being an acute-phase reactant, the level of which increased several-fold after trauma.

Publication types

  • Case Reports
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Amino Acid Sequence
  • Antithrombin III / analysis
  • Antithrombin III / genetics*
  • Arginine / analysis
  • Genetic Variation
  • Hemorrhagic Disorders / enzymology*
  • Hemorrhagic Disorders / therapy
  • Humans
  • Male
  • Methionine / analysis
  • Mutation*
  • Pancreatic Elastase / antagonists & inhibitors
  • Plasma Exchange
  • Wounds and Injuries / complications
  • alpha 1-Antitrypsin / analysis
  • alpha 1-Antitrypsin / genetics*


  • alpha 1-Antitrypsin
  • alpha 1-antitrypsin Pittsburgh
  • Antithrombin III
  • Arginine
  • Methionine
  • Pancreatic Elastase