[Study on secondary structure and properties of alpha- and gamma-forms of human thrombin].
Secondary structure and enzymatic properties of human a-thrombin and its gamma-form (obtaining during autolysis of the native enzyme) have been studied by differential scanning calorimetry (DSC) and circular dichroism (CD). According to DSC-data both alpha-thrombin and gamma-thrombin contained only one thermal transition peak at 58.5 and 53.3 degrees C, respectively. A comparison of these values suggested that gamma-form is less stable than initial a-thrombin. In contrast to that the thermogram of DIP-a-thrombin had two peaks (57.5 and 64.5 degrees C). CD spectra showed that conversion a- to gamma-thrombin influenced the secondary structure of the enzyme slightly. The study of the inhibitory effect of such polyanions as ATP and dextran sulfate (DS) upon thrombin-catalyzed cleavages of fibrinogen has shown that the growth of the negative charge of the polyanion molecule resulted in the increase of its inhibitory activity. The catalytically non-active DIP-alpha-thrombin, which retained the native anion-binding exosite 1, was shown to decrease the inhibitory power of the dextran sulfate. It was explained by competition of DS with the exosite 1 of both alpha- and DIP-alpha -thrombin. In contrast to that DIP-gamma-thrombin having exosite 1 destroyed neither competed nor influenced the anticoagulant capacity of dextran sulfate toward the native alpha-thrombin. In accordance with our data thrombin consists of two rather strong interacting domains. It was shown further that its anion-binding exosite 1 may play a significant role in the interaction of the enzyme with dextran sulfate.
Shvachko
L P
LP
Litvinovich
S V
SV
Kibirev
V K
VK
D002152:Calorimetry, Differential Scanning; D002942:Circular Dichroism; D006801:Humans; D008024:Ligands; D011489:Protein Denaturation; D020033:Protein Isoforms / Q000737:chemistry; D017433:Protein Structure, Secondary; D013696:Temperature; D013816:Thermodynamics; D013917:Thrombin / Q000737:chemistry*
D008024:Ligands; D020033:Protein Isoforms; D013917:Thrombin