Table I. Kinetics of inhibition of fXIa activity by active site inhibitors and by fIX/fIXai.

Kinetics of inhibition were determined from initial velocity measurements using eight concentrations of S2366 or seven concentrations of fIX. Values for K_m and k_cat for cleavage of S2366 or fIX were fixed for the purpose of determining, α, β and K_i, and K* in inhibition models. α and β were derived from the general hyperbolic mixed-type inhibition model (41) and were fixed when determining K* in the two-step model. All ranges are ± 2 standard deviations (95% confidence intervals).

Substrate	Inhibitor	Inhibition type	Km	kcat	α	β	Ki	K*
			μM	s−1			μM
S2366	None		233 ± 78	117 ± 10
S2366	pAB	Competitive	233 ± 78	117 ± 10			28 ± 2
S2366	aprotinin	Competitive	233 ± 78	117 ± 10			1.13 ± 0.07
S2366	fIX	Mixed hyperbolic	233 ± 78	117 ± 10	2.7 ± 0.4	0.5 ± 0.1	0.22 ± 0.05
S2366	fIX	Two step conformational	233 ± 78	117 ± 10	2.7 ± 0.4	0.5 ± 0.1		≥5
S2366	fIXai	Mixed hyperbolic	233 ± 78	117 ± 10	2.5 ± 0.2	0.9 ± 0.1	0.11 ± 0.02
S2366	fIXai	Two step conformational	233 ± 78	117 ± 10	2.5 ± 0.2	0.9 ± 0.1		≥5
FIX	None		0.09 ± 0.04	0.49 ± 0.05
FIX	Aprotinin	Non-competitive	0.09 ± 0.04	0.49 ± 0.05	6.3 ± 4.1	0	0.89 ± 0.52
FIX	fIXai	Competitive	0.09 ± 0.04	0.49 ± 0.05			0.33 ± 0.05