Regulation of activated protein C by thrombin-modified protein S.

J-STAGE
  • SUZUKI Koji
    Department of Laboratory Medicine, Mie University School of Medicine
  • NISHIOKA Junji
    Department of Laboratory Medicine, Mie University School of Medicine
  • HASHIMOTO Senichiro
    Department of Laboratory Medicine, Mie University School of Medicine

書誌事項

公開日
1983
公開者
The Japanese Biochemical Society

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説明

Protein S, a vitamin K-dependent plasma protein having Gla-residues, increases the rate of inactivation of Factor Va by activated protein C by enhancing the binding of activated protein C to phospholipid [Walker, J. F. (1981) J. Biol. Chem. 256, 11128-11131]. The present study aimed at elucidating the effect of thrombinmodified protein S on Factor Va inactivation by activated protein C. Nondigested protein S consisted 81% of intact form and 19% of modified form, and thrombindigested protein S had 96% modified form. Protein S, both nondigested and digested, did not show any effects on the amidolytic activity of activated protein C towards synthetic peptide substrate. Nondigested protein S stimulated the Factor Va inactivation by activated protein C, whereas the digested protein appeared to suppress the inactivation. Protein-phospholipid binding experiments showed that although nondigested protein S enhanced the binding of activated protein C to phospholipid stoichiometrically, digested protein S appeared to not only suppress the complex formation, but also dissociate the complex. This evidence suggested that protein S modified by thrombin regulates the action of activated protein C towards Factor Va on phospholipid.

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