Kinetic parameters for FIXa-catalyzed activation of FX
| Enzyme . | Km (nM) . | kcat (s–1) . | kcat/Km (nM–1 s–1) . | Catalytic efficiency (average fold enhancement) . |
|---|---|---|---|---|
| FIXa | 81 × 103 | 1 × 10–3 | 0.01 × 10–6 | 1 |
| FIXa + FVIIIa | 2-34 × 103 | 0.4-1 × 10–3 | 0.01-0.5 × 10–6 | 25 |
| FIXa + lipids | 90-940 | 0.08-2 × 10–3 | 0.01-22 × 10–6 | 1 000 |
| FIXa + FVIIIa + lipids (tenase complex) | 9-190 | 0.6-29 | 0.1-3 | 155 000 000 |
| Enzyme . | Km (nM) . | kcat (s–1) . | kcat/Km (nM–1 s–1) . | Catalytic efficiency (average fold enhancement) . |
|---|---|---|---|---|
| FIXa | 81 × 103 | 1 × 10–3 | 0.01 × 10–6 | 1 |
| FIXa + FVIIIa | 2-34 × 103 | 0.4-1 × 10–3 | 0.01-0.5 × 10–6 | 25 |
| FIXa + lipids | 90-940 | 0.08-2 × 10–3 | 0.01-22 × 10–6 | 1 000 |
| FIXa + FVIIIa + lipids (tenase complex) | 9-190 | 0.6-29 | 0.1-3 | 155 000 000 |
The catalytic efficiency (kcat/Km) of FIXa toward FX was determined in the presence of Ca2+ ions and FIXa, in the absence of anionic phospholipids; FIXa + FVIIIa, with FVIIIa; FIXa + lipids, in the presence of anionic phospholipids; FIXa + FVIIIa + lipids (tenase complex), when assembled with FVIIIa, Ca2+ ions, and anionic phospholipids into the tenase complex. The tabulated ranges are based on earlier studies.27,97,128-131