Effect of alanine insertion (P′5) on the reactive centre of α1‐antitrypsin

A recombinant mutant of α1‐antitrypsin with an inserted alanine in position P′1 (362=363) was compared with wild‐type recombinant and plasma α1‐antitrypsins. Initial studies showed that contrary to other reports the wild recombinant inhibitor had the same, or even greater, association constants with trypsin and clastasex as the plasma inhibitor. The recombinant mutant as predicted had decreased inhibitory activity but no significant alteration in denaturation temperature and it retained the typical serpin S‐R change.