[Anticlotting activity of fragment D from fibrinogen and fibrin and its dependence on calcium presence when fragments are obtained from fibrinogen].
The CaCl2 concentration of about 10(-4) M slightly reduces the proteolytic fibrinogen degradation and greatly increases the anticlotting activity in the arising fragments D. With a rise in the CaCl2 concentration to 10(-2) M a subsequent limitation of proteolysis occurs, but less active fragments D are formed. These facts suggest that a moderate restriction of peptide bond cleavage enhances the fragment D activity, whereas excessive restriction exhibits an adverse effect. Fragment D originating from noncross-linked fibrin inhibits clotting stronger than its counterpart--the fibrinogen derivative. The following explanation seems plausible. Certain sites of the intact molecules, essential for the inhibitory activity of the prospective fragment D, become somewhat "enzyme-proof" (due to intermolecular links characteristic of polymeric fibrin), thus, avoiding proteolytic damage. Calcium ions presented at the optimum concentration may act similarly.
D001665:Binding Sites; D002118:Calcium / Q000494:pharmacology*; D005338:Fibrin Fibrinogen Degradation Products / Q000494:pharmacology*; D006385:Hemagglutination Inhibition Tests; D006801:Humans; D007700:Kinetics; D011485:Protein Binding
D005338:Fibrin Fibrinogen Degradation Products; D002118:Calcium
Antipolimerizatsiĭna aktivnist' frahmenta D z fibrinohenu ĭ fibrinu ta zalezhnist' ii vid naiavnosti kal'tsiiu pri oderzhanni frahmentiv iz fibrinohenu