The proteolytic activation of partially purified F.IX induced by F.XIa/Ca
2+ was investigated in the patients with hemophilia B variants. When partially purified normal F.IX (BaCl
2 adsorption and elution) was cleaved by F.XIa/Ca
2+, a polypeptide band (MW=60,000) disappeared with the concordant appearance of a peptide with MW=50,000 (F.IXaβ) on SDS gel autoradiography in the absence of reducing agent. In the presence of reducing agent, a new band with MW=30,000 (heavy chain of F.IX) was observed. F.IX (Niigata) and F.IX (Kiryu) with Hemophilia B
M were cleaved by F.XIa/Ca
2+ at the rate similar to normal F.IX. F.IX (Takatsuki) with Hemophilia B
M was slowly cleaved by F.XIa/Ca
2+ compared to normal F.IX. When F.IX (Kashihara) was activated by F.XIa/Ca
2+, no new band was seen in non-reducing gels, whereas only one new band appeared in reducing gels, corresponding to MW=40,000. These showed that F.IX (Kashihara) was cleaved only at Arg-Ala bond and not at Arg-Val bond. F.IX (Nagoya I), F.IX (Nagoya II) and F.IX (R) were not cleaved by F.XIa/Ca
2+ in this system. The proteolytic activation of partially purified F.IX induced by F.XIa/Ca
2+ was investigated in the patients with Hemophilia B variants using western blotting technique.
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