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. Author manuscript; available in PMC: 2014 Jun 1.
Published in final edited form as: J Thromb Haemost. 2013 Jun;11(0 1):265–276. doi: 10.1111/jth.12217

Figure 8. A New Rate-Limiting Step in the Conversion of Prothrombin to Thrombin.

Figure 8

Initial cleavage of prothrombin following Arg320 yields a zymogen-like form (mIIa’) that interconverts slowly and reversibly with the proteinase-like form (mIIa). Because the proteinase-like conformation is required for further cleavage at Arg271, it is only mIIa rather than mIIa’ that is processed to thrombin. The reversible conversion of mIIa’ to mIIa there represents a previously unanticipated rate-limiting step in thrombin formation.