in the presence of ca2+ and phospholipid , the factor xa formed catalyses ( a ) the cleavage of a small peptide ( mol.wt . 4000 ) from the c-terminal region of the heavy chain of factor xa , resulting in a second active form ( mol.wt . 50000 ) , and ( b ) the cleavage of a peptide containing the active-site serine residue ( mol.wt . 13000 ) from the c-terminal region of the heavy chain of factor x , resulting in an inactivatable component ( mol.wt . 59000 ) .
C0015520
factor xa
C0015518
factor x