[Activation by heparin-Sepharose of prothrombin conversion to prethrombin 1]

Using affinity chromatography on heparin-Sepharose, homogeneous prothrombin containing no factor Xa or thrombin was separated into three components differing in their affinities for the bioadsorbent. The major component 2 eluted with 0.35 M NaCl was found to contain prothrombin (Mr 80000) and prethrombin 1 (Mr 60000). Component 1 not bound by heparin contained fragment 1 of prothrombin (Mr 25 000), whereas component 3 with a higher affinity for the bioadsorbent contained factor IX (Mr 52 000). Rechromatography of component 2 provided further evidence for prothrombin modification to prethrombin 1 by heparin-Sepharose. Blocking of endogenous thrombin of prothrombin by diisopropylfluorophosphate did not affect the modification. Heparin-Sepharose probably induced changes in prothrombin conformation and the formation of a catalytic center responsible for prothrombin splitting to prethrombin 1. Heparin-Sepharose can be used for separation of prothrombin proteolytic products by thrombin and for isolation of prethrombin 1 and prothrombin fragment 1.