Dramatic enhancement of the catalytic activity of coagulation factor IXa by alcohols.
The coagulation factor IXa (FIXa) exhibits a very weak proteolytic activity towards natural or synthetic substrates. Upon complex formation with its cofactor FVIIIa and Ca2+-mediated binding to phospholipid membranes, FIXa becomes a very potent activator of FX. The presence of FVIIIa has no effect on the cleavage of peptide substrates by FIXa, however. We found that several alcohols dramatically enhance the catalytic activity of human FIXa towards synthetic substrates. Substrates with the tripeptidyl moiety R-D-Xxx-Gly-Arg are especially susceptible to the enhanced FIXa catalysis. Maximal increase up to 20-fold has been measured in the presence of ethylene glycol. We suggest that alcohols modify the conformation of FIXa rendering the active-site cleft more easily accessible to tripeptide substrates with a hydrophobic residue in the P3-position.
Sturzebecher
J
J
Zentrum fur Vaskulare Biologie und Medizin Erfurt, Friedrich-Schiller-Universität Jena, Erfurt, Germany. stuerze@zmkh.ef.uni-jena.de
Kopetzki
E
E
Bode
W
W
Hopfner
K P
KP
D000438:Alcohols / Q000737:chemistry*; D002384:Catalysis; D018360:Crystallography, X-Ray; D019855:Ethylene Glycol; D005026:Ethylene Glycols / Q000737:chemistry; D015949:Factor IXa / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D011487:Protein Conformation; D012997:Solvents / Q000737:chemistry; D013379:Substrate Specificity
D000438:Alcohols; D005026:Ethylene Glycols; D012997:Solvents; D015949:Factor IXa; D019855:Ethylene Glycol