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. Author manuscript; available in PMC: 2010 Jun 14.
Published in final edited form as: Biochemistry. 2008 Jan 11;47(5):1326–1335. doi: 10.1021/bi701594j

Table 4.

Kinetics of FIX Activation by FXIaa

protein Km
(nM)		 kcat
(min−1)		 fold-change
in kcatb
FXIaWT 268 ± 25 21.816 ± 2.160 1b
FXIaG193A 226 ± 33 2.782 ± 0.052 8
FXIaG193V 167 ± 17 0.021 ± 0.003 1091
FXIaG193D 258 ± 28 0.026 ± 0.003 853
FXIaG193E 236 ± 33 0.048 ± 0.005 455
FXIaG193K 256 ± 31 0.055 ± 0.006 397
a

The rate of FIX activation was determined by measuring the amount of radioactive peptide released at various times in incubations with FXIa, as described under Experimental Procedures. Each reaction was carried out in TBS containing 0.5 mg/mL BSA and 5 mM CaCl2 at 37 °C, with concentrations of FIX varying from 25 to 775 nM, and FXIa concentrations varying from 0.25 to 25 nM. The data are normalized to 25 nM FXIa.

b

Fold-change is compared to FIX activation by FXIaWT.