The Conversion of Prothrombin to Thrombin

prothrombin activation by activated Factor X and Ca2+ in the presence of phospholipid also proceeds via Intermediate 2 and Fragment 1.2, i.e.INTERMEDIATE 2 ,%OTHROMBlN + + [ 1 THROMBIN d + 1) FRAGMENT 1.2 FRAGMENT 1'2 Unless rapidly inactivated, thrombin cleaves Fragment 1.2 into two smaller activation products, i.e.THROMBIN FRAGMENT l-2 -FRAGMENT 1 + FRAGMENT 2 2)The direct and concomitant formation of Intermediate 2 and Fragment 1.2 was demonstrated by activating prothrombin in the presence of iPrzP-F.In the absence of this inhibitor, thrombin, in addition to catalyzing the reaction of Equation 2, cleaves Fragment 1 from prothrombin and in so doing eliminates the possibility of observing phospholipid catalysis from all but the earliest stages of reaction (GITEL,