Definitions of A1PI

  1. Plasma glycoprotein member of the serpin superfamily which inhibits trypsin, neutrophil elastase, and other proteolytic enzymes. Commonly referred to as alpha 1- proteinase inhibitor ( A1PI), it exists in over 30 different biochemical variant forms known collectively as the Pi ( protease inhibitor) system. Hereditary A1PI deficiency is associated with pulmonary emphysema.