Dissociation of the thrombin/antithrombin III reaction from amidolytic activity of the enzyme at high salt concentration.
Amidolytic activity of thrombin increased proportionally with NaCl concentrations up to 1 M NaCl, due to an increase in the turnover rate with no change in the Km of the enzyme. Neutralization of thrombin by antithrombin III (AT III) was maximum in 0.1 to 0.15 M NaCl, but completely absent at high NaCl concentrations. Moreover, ratio of rates of the amidolytic activity of thrombin to of the enzyme/AT III reaction was not constant at several pHs. The rate of the thrombin/AT III reaction appeared to be inversely correlated with the enzyme's stability. Therefore, it was concluded that some factor(s) other than the active site of the thrombin molecule was more important in its primary interaction with AT III.
Oshima
G
G
School of Pharmaceutical Sciences, Kitasato University, Tokyo, Japan.
D000990:Antithrombin III / Q000502:physiology*; D006863:Hydrogen-Ion Concentration; D012965:Sodium Chloride / Q000494:pharmacology; D013917:Thrombin / Q000037:antagonists & inhibitors*
D012965:Sodium Chloride; D000990:Antithrombin III; D013917:Thrombin