Activation of recombinant human FVIII by thrombin mutants.

A 2-step chromogenic assay was used to screen the ability of WT and mutant thrombins to activate recombinant human FVIII, as described in “Materials and methods.” The effect of alanine substitution on FVIII activation is shown relative to 100% WT activity, with error bars representing the standard deviation for at least 2 individual experiments performed in duplicate. Single-letter amino acid codes have been used in this figure for spatial considerations.