Table 2.
Enzyme kinetic parameters for the recombinant SbNIT4A/B1 and SbNIT4A/B2 heterocomplexes
| Compound |
SbNIT4A/B1 |
SbNIT4A/B2 |
||
|---|---|---|---|---|
| Km, mM | Vmax, nkat (mg protein)−1 | Km, mM | Vmax, nkat (mg protein)−1 | |
| β-Cyanoalanine* | 0.86 ± 0.14 | 308 ± 51 | 0.89 ± 0.26 | 432 ± 32 |
| 2-Phenylacetonitrile | n.d. | n.d. | 0.19 ± 0.03 | 908 ± 108 |
| 4-Hydroxyphenylacetonitrile | n.d. | n.d. | 0.17 ± 0.01 | 940 ± 249 |
| Indole-3-acetonitrile | n.d. | n.d. | 0.16 ± 0.01 | 323 ± 31 |
The active enzyme component (SbNIT4A for β-cyanoalanine and SbNIT4B2 for the other substrates) was combined in a 1:10 ratio with the second enzyme component to favor that a high proportion of the active component was present in heterocomplexes. Shown are the means ± SD from two to three independent experiments performed in triplicate.
*Only nitrilase activity (release of NH4+) was measured. The total activity is 3- to 4-fold higher because of the high nitrile hydratase activity of the enzymes for this substrate (see text).
n.d., not determined.