Biochemical characterization of bovine plasma thrombin-activatable fibrinolysis inhibitor (TAFI).
BACKGROUND
TAFI is a plasma protein assumed to be an important link between coagulation and fibrinolysis. The three-dimensional crystal structures of authentic mature bovine TAFI (TAFIa) in complex with tick carboxypeptidase inhibitor, authentic full lenght bovine plasma thrombin-activatable fibrinolysis inhibitor (TAFI), and recombinant human TAFI have recently been solved. In light of these recent advances, we have characterized authentic bovine TAFI biochemically and compared it to human TAFI.


RESULTS
The four N-linked glycosylation sequons within the activation peptide were all occupied in bovine TAFI, similar to human TAFI, while the sequon located within the enzyme moiety of the bovine protein was non-glycosylated. The enzymatic stability and the kinetic constants of TAFIa differed somewhat between the two proteins, as did the isoelectric point of TAFI, but not TAFIa. Equivalent to human TAFI, bovine TAFI was a substrate for transglutaminases and could be proteolytically cleaved by trypsin or thrombin/solulin complex, although small differences in the fragmentation patterns were observed. Furthermore, bovine TAFI exhibited intrinsic activity and TAFIa attenuated tPA-mediated fibrinolysis similar to the human protein.


CONCLUSIONS
The findings presented here suggest that the properties of these two orthologous proteins are similar and that conclusions reached using the bovine TAFI may be extrapolated to the human protein.
Valnickova
Zuzana
Z
Center for Insoluble Protein Structures and Interdisciplinary Nanoscience Center, Department of Molecular Biology, Science Park, University of Aarhus, Gustav Wieds Vej 10c, 8000 Aarhus C, Denmark. zv@mb.au.dk
Thaysen-Andersen
Morten
M
Højrup
Peter
P
Christensen
Trine
T
Sanggaard
Kristian W
KW
Kristensen
Torsten
T
Enghild
Jan J
JJ
D000818:Animals; D025901:Carboxypeptidase B2 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D002417:Cattle; D002851:Chromatography, High Pressure Liquid; D004591:Electrophoresis, Polyacrylamide Gel; D004795:Enzyme Stability; D005342:Fibrinolysis; D006031:Glycosylation; D006801:Humans; D007526:Isoelectric Point; D007527:Isoenzymes / Q000737:chemistry / Q000378:metabolism; D007700:Kinetics; D008970:Molecular Weight; D010446:Peptide Fragments / Q000378:metabolism; D011134:Polysaccharides / Q000737:chemistry / Q000378:metabolism; D013379:Substrate Specificity; D013696:Temperature; D014357:Trypsin / Q000378:metabolism
D007527:Isoenzymes; D010446:Peptide Fragments; D011134:Polysaccharides; D025901:Carboxypeptidase B2; D014357:Trypsin