Kinetic study on the initial stage of the fibrinogen-fibrin conversion by thrombin. (II) Application of enzyme kinetics to turbidimetrical method.

The kinetic treatment of the initial stage of the fibrinogen-fibrin conversion, reported in our preceding paper, was improved. Presuming zero turbidity in the induction period, Ip, of turbidity-time curves, the zero concentration of fibrin monomer at the end of induction period was considered to be constant. At that time, the formation velocity of such smallest polymers of fibrin monomer as detectable by turbidimetry was represented by an equation similar to an equation described in the enzyme kinetics. The constant, Kmp, derived from our equation, corresponding to the Michaelis-Menten constant to be 1.79 X 10(-6) M, which is somewhat smaller than the Michaelis-Menten constant of proteolysis of fibrinogen by thrombin. Thus, it was concluded that practical and handy kinetic assay was possible on the initial stage of the fibrinogen-fibrin conversion.