Alpha1-antitrypsin, 52kDa, is the prototypic member of the serine protease inhibitor (serpin) superfamily, which have a major role in inactivating neutrophil elastase and other proteases to maintain protease-antiprotease balance. The protein is synthesized mainly in the liver, but exerts its main function in the lung where it inhibits a variety of serine proteases, but primarily neutrophil elastase. It provides more than 90% of the antiproteolytic shield of the lower respiratory tract protecting the elastic tissue from degradation. Disorders of the enzyme include alpha 1-antitrypsin deficiency, a hereditary disorder in which lack of alpha 1-antitrypsin leads to uninhibited tissue breakdown during inflammation. This causes pulmonary emphysema and leads to liver cirrhosis in severe cases.