TABLE 3.
Specific activities of phenylhydantoinase and allantoinase from E. coli for different substrates
| Substrate | Enzyme activity (U)a
|
|
|---|---|---|
| Phenylhydantoinase | Allantoinase | |
| Hydroxyphenylhydantoin | 3.29 | ND |
| Phenylhydantoin | 2.93 | ND |
| Isopropylhydantoin | 0.85 | 0.02 |
| Hydantoin | 0.37 | 0.12 |
| Dihydrothymine | NDb | ND |
| Uracil | ND | ND |
| 5-Bromouracil | 0.08 | 0.01 |
| Dihydrouracil | ND | ND |
| Dihydroorotate | ND | ND |
| Allantoin | ND | 6.59 |
a
Enzyme activity was determined by adding the purified enzyme (10 μg) to the reaction mixture containing 1 ml of 100 mM Tris-HCl (pH 8.0) buffer and 10 mM substrate. The reaction products were analyzed by using either HPLC or the colorimetric method as described in Materials and Methods. Each value represents the average of three independent assays.
b
ND, not detected under specified experimental conditions.