Bikunin - not just a plasma proteinase inhibitor

Bikunin is a plasma proteinase inhibitor that has received little attention in the past, probably because its activity towards various proteinases was found to be relatively weak in early work. It was recently discovered, how ever, that bikunin effectively inhibits a proteinase that seems to be invol ved in the metastasis of tumour cells - cell surface plasmin - and that a f ragment of bikunin inhibits two proteinases of the coagulation pathway - fa ctor X-a and kallikrein. Furthermore, it has been found that bikunin has ot her properties, such as the ability to modulate cell growth and to block ce llular calcium uptake. Most of the bikunin in the blood occurs as a covalen tly linked subunit of the proteins pre- and inter-alpha-inhibitor. In this form bikunin lacks some of its known activities, and there is evidence that its release by partial proteolytic degradation may function as a regulator y mechanism. Although the physiological function of bikunin still remains t o be established, current data suggest that this protein plays a role in in flammation. Further studies could therefore lead to results of therapeutica l value. (C) 2000 Elsevier Science Ltd. All rights reserved.