Table 2. MSD proteins and their retro-aldolase activity.
| Name | Catalytic triad | Number of mutations compared to ssIGPS | Conversion rate (s-1) |
kcat/KM (M-1s-1) |
|---|---|---|---|---|
| RA_MSD1 | K210 D131 S110 | 21 | 8.08 × 10−7 | ND |
| RA_MSD2 | K210 D131 S110 | 22 | 3.14 × 10−7 | ND |
| RA_MSD2.4 | K210 D131 S110 | 26 | 1.23 × 10−6 | ND |
| RA_MSD2.5 | K210 D131 S110 | 29 | 1.49 × 10−6 | ND |
| RA_MSD3 | K210 D131 S110 | 22 | 2.60 × 10−6 | ND |
| RA_MSD4 | K51 E53 S83 | 20 | 3.03 × 10−6 | ND |
| RA_MSD5 | K51 E53 S83 | 21 | 1.69 × 10−5 | 3.47 × 10−2 |
| RA_MSD6 | K231 E53 S83 | 25 | 2.82 × 10−6 | ND |
| RA_MSD7 | K231 E131 T159 | 18 | 8.33 × 10−6 | 1.41 × 10−2 |
| RA_MSD8 | K231 E131 T159 | 18 | 5.61 × 10−6 | ND |
| RA_MSD9 | K231 E53 T83 | 19 | 7.55 × 10−7 | ND |
The catalytic triad designed for nine proteins (RA_MSD1—RA_MSD9) is specified in the second column. The third column gives the number of residue exchanges compared to the native sequence of ssIGPS. The fourth column lists the conversion rates (rate of product formation divided by the enzyme concentration) in the presence of 500 μM S-methodol. The last column gives the catalytic efficiency kcat/KM as determined for RA_MSD5 and RS_MSD7 from the linear part of substrate saturation curves; see S1 Fig. ND: not determined.