title: The role of human factor X activation peptide in activation of factor X by factor IXa.
abstract: We studied the interaction of factor X activation peptide (XAP) with factor IXa and factor Xa and the effect of XAP on factor IXa-catalyzed activation of factor X. XAP associated with factor Xa in the presence of 5 mM Ca2+ was dissociated from factor Xa by gel chromatography using Ultrogel AcA54 in 5 mM EDTA, or in 8 M urea-0.1% SDS. An exogenous isolated XAP inhibited the factor IXa-catalyzed factor X activation both in the presence and absence of factor VIIIa. 4-Amidinophenylmethylsulfonyl (aPMS)-factor Xa independent of XAP also inhibited the factor X activation more effectively than XAP alone in the presence of factor VIIIa. However, aPMS-factor Xa independent of XAP hardly inhibited the factor X activation in the absence of factor VIIIa. The binding of 125I-labeled factor X to the aPMS-factor IXa fixed to a microwell plate was inhibited by unlabeled factor X or XAP, but not by aPMS-factor Xa with or without XAP. Factor IXa directly bound to XAP and aPMS-factor Xa with XAP, but did not bind to aPMS-factor Xa without XAP. These findings suggest that the region of XAP in factor X directly interacts with factor IXa, and factor Xa region other than XAP interacts with factor VIIIa. Desialation or deletion of N-linked carbohydrates of XAP reduced the inhibitory activity of XAP for the factor X activation by factor IXa to approximately 50% of that of the intact XAP. This suggests that the sialic acids in the carbohydrate chains of the XAP region partly contribute to the interaction with factor IXa during its activation.
authors: Department of Molecular Biology on Genetic Disease, Mie University School of Medicine.
authors: M
authors: M
authors: Iino
authors: H
authors: H
authors: Takeya
authors: J
authors: J
authors: Nishioka
authors: T
authors: T
authors: Nakagaki
authors: K
authors: K
authors: Tamura
authors: K
authors: K
authors: Suzuki
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002417:Cattle; D002845:Chromatography; D015949:Factor IXa / Q000378:metabolism / Q000502:physiology*; D015944:Factor VIIIa / Q000494:pharmacology; D005170:Factor X / Q000378:metabolism / Q000502:physiology*; D015951:Factor Xa / Q000378:metabolism / Q000494:pharmacology / Q000502:physiology*; D006801:Humans; D007457:Iodine Radioisotopes; D008666:Metalloendopeptidases / Q000494:pharmacology; D008969:Molecular Sequence Data; D011817:Rabbits
chemical_list: D007457:Iodine Radioisotopes; D015944:Factor VIIIa; D005170:Factor X; D015949:Factor IXa; D015951:Factor Xa; D008666:Metalloendopeptidases; C033858:russellysin