Plasma protein S activity measured using Protac, a snake venom derived activator of protein C.
Functional activity of protein S, a cofactor of activated protein C-dependent inhibition of blood coagulation, in human plasma was measured by using Protac, a snake venom derived activator of protein C. This assay appeared to be specific for protein S, because 1) the activated partial thromboplastin time of protein S-depleted plasma depended on the purified protein S added in the presence of Protac; and 2) the level of protein C in plasma sample (0 to 10 micrograms/ml) had no influence on the clotting time. The cofactor activity of protein S in the plasma of normal men (n = 16) and women (n = 14) was 99.4 +/- 23.8% and 98.6 +/- 24.5% respectively. The protein S activity in the plasma of pregnant women at pre- and post-partum (n = 14), and that in the plasma of patients under warfarin therapy (n = 20) were 46.2 +/- 18.9%, 45.8 +/- 19.6% and 24.0 +/- 15.7%, respectively. In these plasmas, the levels of protein S activity were lower than those of total protein S antigen, but were similar to those of free protein S antigen. In 16 patients out of two families with congenital protein S deficiency, the protein S activity, the free antigen and the total antigen were 9.4 +/- 6.9%, 13.3 +/- 4.6% and 57.4 +/- 20.7%, respectively. There was no significant relationship between the level of protein S activity and that of a complemental C4b-binding protein antigen in any of these patients.
Suzuki
K
K
Department of Laboratory Medicine, Mie University School of Medicine, Japan.
Nishioka
J
J
D005260:Female; D006023:Glycoproteins / Q000097:blood* / Q000172:deficiency; D006649:Histocompatibility Antigens / Q000032:analysis; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins; D008297:Male; D010455:Peptides / Q000032:analysis / Q000494:pharmacology; D049590:Postpartum Period / Q000097:blood; D011247:Pregnancy / Q000097:blood; D011486:Protein C / Q000502:physiology*; D017293:Protein S; D012016:Reference Values; D012910:Snake Venoms / Q000032:analysis; D014859:Warfarin / Q000627:therapeutic use
D006023:Glycoproteins; D006649:Histocompatibility Antigens; D036341:Intercellular Signaling Peptides and Proteins; D010455:Peptides; D011486:Protein C; D017293:Protein S; D012910:Snake Venoms; C049647:snake venom protein C activator; D014859:Warfarin