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, however, that bikunin effectively inhibits a proteinase that seems to be involved in the metastasis of tumour cells--cell surface plasmin--and that a fragment of bikunin inhibits two proteinases of the coagulation pathway--factor Xa and kallikrein. Furthermore, it has been found that bikunin has other properties, such as the ability to modulate cell growth and to block cellular calcium uptake. Most of the bikunin in the blood occurs as a covalently 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 regulatory mechanism. Although the physiological function of bikunin still remains to be established, current data suggest that this protein plays a role in inflammation. Further studies could therefore lead to results of therapeutical value.
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Department of Medical Biochemistry and Microbiology, Uppsala University, Sweden. erik.fries@medkem.uu.se
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D002118:Calcium / Q000378:metabolism; D002240:Carbohydrate Sequence; D005109:Extracellular Matrix / Q000378:metabolism; D015870:Gene Expression; D006023:Glycoproteins / Q000097:blood* / Q000737:chemistry* / Q000235:genetics; D006133:Growth Substances / Q000097:blood / Q000737:chemistry / Q000235:genetics; D006801:Humans; D007669:Kidney Calculi / Q000517:prevention & control; D008562:Membrane Glycoproteins; D008958:Models, Molecular; D008969:Molecular Sequence Data; D015394:Molecular Structure; D008970:Molecular Weight; D011487:Protein Conformation; D015842:Serine Proteinase Inhibitors / Q000097:blood* / Q000737:chemistry* / Q000235:genetics; D014360:Trypsin Inhibitor, Kunitz Soybean
D006023:Glycoproteins; D006133:Growth Substances; D008562:Membrane Glycoproteins; C109148:SPINT2 protein, human; D015842:Serine Proteinase Inhibitors; D014360:Trypsin Inhibitor, Kunitz Soybean; D002118:Calcium