Table 2.
The kinetic parameters of the examined cleavage reactions.
| Substrate | Enzyme | [E]T (nM) | kobs (s−1) | kobs/[E]T (M−1 s−1) | Approx. relative efficiency |
|---|---|---|---|---|---|
| C3bB | None (background) | – | (1.0 ± 0.1) × 10−6a | – | – |
| FD | 0.25 | (1.6 ± 0.1) × 10−3 | (6.5 ± 0.5) × 106 | 1 | |
| pro-FD-R/Q | 100 | (7.8 ± 0.2) × 10−4 | (7.8 ± 0.2) × 103 | 1/800 | |
| MASP-1cf | 1,000 | (2.3 ± 0.6) × 10−4 | (2.3 ± 0.6) × 102 | 1/30 000 | |
| MASP-3cf | 2,000b | (2.6 ± 1.0) × 10−6 | ∼0.9c | negligible | |
| FB | None (background) | – | ND | – | – |
| FD | 2,000 | (6.4 ± 1.4) × 10−7 | 0.3 ± 0.07 | 1/20,000,000 | |
| pro-FD-R/Q | 2,000 | (2.3 ± 0.7) × 10−7d | ∼0.1c | negligible | |
| MASP-1cf | 2,600 | (6.4 ± 2.3) × 10−6 | 2.5 ± 0.9 | 1/3,000,000 | |
| MASP-3cf | 10,000b | ND | – | – |
The kobs/[E]T value can be considered as an estimate for the catalytic efficiency (kcat/KM). The average ± SD values were determined from three parallels, except when stated otherwise.
ND, no detectable cleavage.
a
The low-level background cleavage was probably due to a trace contaminant in C3b.
b
Approximately 90% active and 10% zymogen.
c
Close to the detection limit defined by the background. Only an approximate kobs/[E]T could be determined.
d
Average ± SD from two parallels.