TABLE 2.
Basal activity, PLP saturation, and AdoMet response of the purified CBS enzymes
The purified enzymes were assayed for CBS catalytic activity in the classical reaction. The saturation of the purified enzyme with PLP cofactor was tested by running the activity assay in the presence or absence of 500 μm PLP. The AdoMet response was determined by assaying the enzyme in the presence or absence of 300 μm AdoMet. The + and − signs denote the presence and absence, respectively, of PLP or AdoMet in the reactions. Values represent average values with S.E. from at least three independent assays.
| CBS specific activity | |||
|---|---|---|---|
| units/mg of protein | |||
| CBS protein | |||
| WT | 128 ± 15 | 148 ± 21 | 530 ± 45 |
| P49L | 117 ± 14 | 122 ± 12 | 388 ± 39 |
| P78R | 97 ± 12 | 110 ± 15 | 501 ± 27 |
| A114V | 92 ± 13 | 100 ± 11 | 401 ± 31 |
| R125Q | 57 ± 10 | 139 ± 18 | 106 ± 9 |
| E176K | 66 ± 11 | 138 ± 14 | 111 ± 8 |
| P422L | 196 ± 20 | 226 ± 28 | 238 ± 41 |
| I435T | 322 ± 37 | 564 ± 44 | 582 ± 60 |
| S466L | 497 ± 31 | 626 ± 48 | 639 ± 43 |
| 500 μm PLP | − | + | + |
| 300 μm AdoMet | − | − | + |