Problems in the assay of thrombin using synthetic peptides as substrates

Abstract

Synthetic tripeptides (code named S-2160 and Chromozym TH) have been used as substrates for the measurement of thrombin activity in two commercial preparations of bovine thrombin, using the International Standard for thrombin (I.S. thrombin) for comparison. The results, when compared to the data obtained using the natural substrate, fibrinogen, indicated the following: 1) the thrombin potency of one commercial thrombin was much higher using the synthetic substrate assays than when the clotting assay was used; the synthetic substrate data for the other commercial thrombin differed significantly from the clotting assay data but in a less consistent manner. 2) the loss of the biological activity of thrombin when stored in frozen aliquots (−20°C) was very rapid, while the amidolytic activity of similarly stored samples did not alter significantly. It was concluded that the synthetic substrates used in this study were of little use when measuring the biological activity of thrombin preparations in comparison to the established standard for thrombin (I.S. thrombin).