inter-α-trypsin inhibitor (ITI, IαI)

The inter-α-trypsin inhibitor (ITI, IαI) family, a typical and classical example for protein-glycosaminogly­canprotein (PGP) complexes, occurs constitutively in plasma at relatively high concentrations and is a result of alternate combinations of three kinds of heavy chains with a common light chain, the bikunin proteoglycan. Bikunin has two proteinase inhibitor domains and belongs to the Kunitz-type protease inhibitor family; it displays an inhibitory activity against trypsin, leukocyte elastase and plasmin. The heavy chains do not have any protease inhibitory properties but have the capacity o interact in vitro and in vivo with hyaluronic acid and this binding promotes the stability of the extra-cellular matrix. The ITI protein family is suspected of playing a key role in the extra-cellular matrix biology.