Table 1 Kinetic parameters defining... | American Society of Hematology

Table 1

Kinetic parameters defining cleavage of prothrombin variants on membrane surfaces*

Prothrombin variant	Available cleavage site	Donor	Activated platelets†			PCPS vesicles
Prothrombin variant	Available cleavage site	Donor	K_m, μM	V_max, nM/s	R²	K_m, μM	V_max, nM/s	R²
rP2	Arg271	1	0.77	4.43	0.970	0.34	2.27	0.935
		2	0.86	0.96	0.990
Mean ± SD			0.82 ± 0.05
rMZ	Arg320	1	2.15	4.50	0.987	0.32	4.72	0.988
		2	1.68	1.37	0.934
Mean ± SD			1.91 ± 0.24

Prothrombin variant	Available cleavage site	Donor	Activated platelets†			PCPS vesicles
Prothrombin variant	Available cleavage site	Donor	K_m, μM	V_max, nM/s	R²	K_m, μM	V_max, nM/s	R²
rP2	Arg271	1	0.77	4.43	0.970	0.34	2.27	0.935
		2	0.86	0.96	0.990
Mean ± SD			0.82 ± 0.05
rMZ	Arg320	1	2.15	4.50	0.987	0.32	4.72	0.988
		2	1.68	1.37	0.934
Mean ± SD			1.91 ± 0.24

K_m and V_max values were determined by titration of rP2 or rMZ and fitting to the Michaelis-Menten equation, as described in “Determination of the kinetic constants governing cleavage at Arg271 and Arg320” and “Data analyses.” The R² values for these fits are indicated. Substrate consumption did not exceed 10% in these experiments. Experiments on PCPS vesicles were performed once.

†

Experiments with activated platelets were performed using platelets from 2 individual donors. Shown are the fit values of K_m and V_max for each individual donor, as well as mean values for K_m.

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