Factor IXa, in a complex with factor VIIIa on the surfaces of activated platelets (the "intrinsic tenase complex"), catalyzes the formation of activated factor X with high efficiency. The amino terminal part of the heavy chain of factor X, the factor X activation peptide, is released. (This peptide has no known function.)
Ahmad, SS, Ashby, B, Walsh, PN, Rawala-Sheikh, R
serine-type endopeptidase activity of factor VIIIa:factor IXa [plasma membrane]
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