biological activity analysis of native and recombinant streptokinase using clot lysis and chromogenic substrate assay

determination of streptokinase activity is usually accomplished through two assay methods: a) clot lysis, b) chromogenic substrate assay. in this study the biological activity of two streptokinase products, namely streptase®, which is a native product and heberkinasa®, which is a recombinant product, was determined against the third international reference standard using the two forementioned assay methods. the results indicated that whilst the activity of streptase® was found to be 101 ± 4% and 97 ± 5% of the label claim with clot lysis and chromogenic substrate assay respectively, for heberkinasa® the potency values obtained were 42 ± 5% and 92.5 ± 2% of the label claim respectively. to shed some light on the reason for this finding, the n-terminal sequence of the streptokinase molecules present in the two products was determined. the results showed slight differences in the amino acid sequence of the recombinant product in comparison to the native one at the amino terminus. this finding supports those of other workers who found that n-terminal sequence of the streptokinase molecule can have significant effect on the activity of this protein.