Determination of Factor X_a Activity by Means of Chromogenic Substrates Based on the Primary Structure of Prothrombin

Through the work of Magnusson and co-workers leading to the elucidation of the primary structure of prothrombin including the amino acid sequences around the two bonds split by factor X_a it has been possible to design a synthetic chromogenic peptide substrate. Bz-Ile-Glu-Gly-Arg-pNA, specifically intended for the determination of factor X_a. Furthermore, additional substrates have been synthezised with various alterations in the amino acid sequence. The activity of factor X_a and other serine proteases within the coagulation and fibrinolytic systems towards these substrates will be discussed with special regard to their possible use in coagulation studies.