A simple functional protein S assay using PROTAC.
Protein S is the co-factor of the enzymic action of protein C on FV and FVIII. A functional assay for protein S is not readily available for clinical use; however, we have developed a functional protein S assay based on the prolongation of Russell viper venom (RVV) plasma clotting time by protein C activated by PROTAC. Based on this assay, median functional protein S (5-95th percentile) of 46 healthy individuals was 82% (60-120%). Median functional protein S of 15 cord blood samples was 58% (35-71%). Unexpectedly, we found relatively high levels of functional protein S in a group of patients on long-term warfarin therapy whose INR ranged from 1.1 to 3.9. The median functional protein S of these patients was 71% (40-101%). We demonstrated that the protein S was not decarboxylated, as was the case with protein C, in these warfarin plasmas.
Han
P
P
Haematology Division Laboratory Medicine, National University Hospital, Singapore.
Pradham
M
M
D005312:Fetal Blood / Q000737:chemistry; D006023:Glycoproteins / Q000097:blood*; D006801:Humans; D007123:Immunoelectrophoresis, Two-Dimensional; D007231:Infant, Newborn; D036341:Intercellular Signaling Peptides and Proteins; D010314:Partial Thromboplastin Time; D010455:Peptides; D011486:Protein C; D017293:Protein S; D011517:Prothrombin Time; D014859:Warfarin / Q000627:therapeutic use
D006023:Glycoproteins; D036341:Intercellular Signaling Peptides and Proteins; D010455:Peptides; D011486:Protein C; D017293:Protein S; C049647:snake venom protein C activator; D014859:Warfarin