Protein C in bovine plasma after warfarin treatment. Purification, partial characterization, and beta-hydroxyaspartic acid content.

Protein C was purified from the plasma of a cow treated with the vitamin K antagonist warfarin. The purified protein appeared not to bind Ca2+ ions in contrast to protein C from an untreated animal. The gamma-carboxyglutamic acid content of the abnormal protein C was reduced to approximately 10% of normal, whereas the beta-hydroxyaspartic acid content was only slightly decreased, suggesting that vitamin K is not involved in the postribosomal hydroxylation of the aspartic acid residue in position 71 of the light chain of protein C. The abnormal and normal proteins were activated at the same rates by thrombin, but normal protein C was more rapidly activated by the thrombin-thrombomodulin complex. Compared to normal protein C, the abnormal one had virtually no anticoagulant activity.