Biochemical characterisation of genetically variant and abnormal blood coagulation factor XIII A subunits.

The products of the FXIIA*1 and FXIIIA*2 alleles were purified and compared for their substrate specificities, heat stability and pH optima. Although some differences were apparent in the heat stability and pH optima of the purified protein, the differences were not apparent in unpurified plasma samples. It, therefore, appears that there are no physiologically important differences between the products of the two alleles. The unpurified product of the FXIIIA*3 allele was compared for its pH optimum and heat stability with unpurified plasma samples of the other two alleles. The pH optimum of the Type 3 A subunits was pH 9.10 compared to pH 8.38 for the Type 1 and Type 2 A subunits. In addition, The Type 3 A subunits were more rapidly heat inactivated.