The interplay of human plasma alpha-1-antichymotrypsin with serine proteinases from totally different tissues has been investigated. The protein was discovered to kind steady complexes with pancreatic chymotrypsin, leukocyte cathepsin G, and mast cell chymotrypsin. No inhibition of pancreatic trypsin or leukocyte elastase may very well be demonstrated. With mixtures containing each alpha-1-antichymotrypsin and alpha-1-proteinase inhibitor, it was discovered that the previous preferentially inactivated leukocyte cathepsin G, whereas the latter confirmed a robust choice for pancreatic chymotrypsin.

However, leukocyte elastase was particularly inactivated by alpha-1-proteinase inhibitor even in 1:1 mixtures with chymotrypsin. All of those outcomes taken collectively recommend that one of many main capabilities of alpha-1-antichymotrypsin is to inactivate leukocyte cathepsin G, whereas alpha-1-proteinase inhibitor controls the exercise of different serine proteinases, significantly leukocyte elastase.