Heparin-catalyzed factor Xa or prothrombinase inhibition by the mutant of antithrombin
| . | − Cofactor . | + PC/PS . | + PC/PS + Va . |
|---|---|---|---|
| H5 | (1.1 ± 0.1) × 105 | (8.2 ± 0.2) × 104 | (1.8 ± 0.4) × 104 |
| H26 | (3.6 ± 0.3) × 105 | (3.3 ± 0.3) × 105 | (2.0 ± 0.4) × 105 |
| H70 | (1.0 ± 0.1) × 107 | (2.1 ± 0.1) × 107 | (1.8 ± 0.1) × 106 |
| UFH | (8.5 ± 0.5) × 106 | (1.0 ± 0.1) × 107 | (6.7 ± 0.8) × 105 |
| . | − Cofactor . | + PC/PS . | + PC/PS + Va . |
|---|---|---|---|
| H5 | (1.1 ± 0.1) × 105 | (8.2 ± 0.2) × 104 | (1.8 ± 0.4) × 104 |
| H26 | (3.6 ± 0.3) × 105 | (3.3 ± 0.3) × 105 | (2.0 ± 0.4) × 105 |
| H70 | (1.0 ± 0.1) × 107 | (2.1 ± 0.1) × 107 | (1.8 ± 0.1) × 106 |
| UFH | (8.5 ± 0.5) × 106 | (1.0 ± 0.1) × 107 | (6.7 ± 0.8) × 105 |
Human factor Xa (1 nM) alone or in complex with human factor Va (5 nM) on 50 μM PC/PS vesicles was incubated with 500 nM antithrombin and catalytic levels of heparin (1-25 nM) in TBS buffer containing 1 mg/mL BSA, 0.1% PEG 8 000, and 2.5 mM CaCl2. Second-order inhibition rate constants (M−1 second−1) were determined from the time-dependent decrease of factor Xa activity toward hydrolysis of Spectrozyme Fxa, as described in “Materials and methods.”
PC/PS indicates phosphatidylcholine/phosphatidylserine; H5, pentasaccharide; H26, approximately 26-saccharide high-affinity heparin; H70, approximately 70-saccharide high-affinity heparin; UFH, unfractionated heparin; BSA, bovine serum albumin.