Which activated coagulation factor is NOT classified as a serine protease?

Factor VIII is the factor among the options that is not classified as a serine protease. Serine proteases are enzymes that have a serine residue in their active site and are involved in the proteolytic cleavage of other proteins, which is a key function in the coagulation cascade.

Factor VIII, on the other hand, functions primarily as a cofactor in the activation of Factor X but does not possess proteolytic activity itself. It assists and stabilizes other coagulation factors rather than cleaving them. Coagulation Factors X, IX, and VII, however, are all classified as serine proteases, as they directly cleave and activate other proteins within the coagulation pathway.

Understanding this classification is important in hematology since it highlights the different roles that various factors play in coagulation, with some directly participating in the enzyme activities while others serve supportive or regulatory roles.