EC Number   |
Natural Substrates |
|---|
    4.2.1.17 | (2E)-5-methylhexa-2,4-dienoyl-CoA + H2O |
- |
| 4.2.1.17 | (3S)-3-hydroxyacyl-CoA |
- |
| 4.2.1.17 | (S)-3-hydroxybutyryl-CoA |
- |
| 4.2.1.17 | (Z)-2-butenoyl-CoA + H2O |
kcat is 12fold slower than with the trans-iosmer crotonyl-CoA |
| 4.2.1.17 | 2,3-didehydroadipyl-CoA + H2O |
- |
| 4.2.1.17 | 4-(N,N-dimethylamino)cinnamoyl-CoA + H2O |
- |
| 4.2.1.17 | crotonoyl-CoA + H2O |
- |
| 4.2.1.17 | crotonyl-CoA + H2O |
- |
| 4.2.1.17 | crotonyl-CoA + H2O |
i.e. (E)-2-butenoyl-CoA. The reaction proceeds via the syn addition of water and thus the pro-2R proton of (3S)-hydroxybutyryl-CoA is derived from solvent. The equilibrium constant for the hydration of trans-2-crotonyl-CoA to (3S)-hydroxybutyryl-CoA is 7.5. The rate of 3(R)-hydroxybutyryl-CoA formation is 400000fold slower than the normal hydration reaction (of crotonyl-CoA to (3S)-3-hydroxybutanoyl-CoA) but at least 1600000fold faster than the non-enzyme-catalyzed reaction. Formation of the incorrect stereoisomer likely occurs via syn addition of water to the incorrect face of the trans-2-crotonyl-CoA double bond. The absolute stereospecificity for the enzyme-catalyzed reaction is 1 in 400000. To account for the exchange of the hydroxybutyryl pro-2S proton, the enzyme must also catalyze the dehydration of 3(R)-hydroxybutyryl-CoA to cis-2-crotonyl-CoA. Thus, the enzyme is capable of catalyzing the epimerization of hydroxybutyryl-CoA |
| 4.2.1.17 | crotonyl-CoA + H2O |
two enoyl coenzyme A hydrases ocur in Rhodospirillum rubrum extracts whose combined activity results in the racemization of (3S)-3-hydroxybutanoyl-CoA to (3R)-3-hydroxybutanoyl-CoA. Both hydrases catalyze the reversible hydration of crotonyl coenzyme A to 3-hydroxybutanoyl coenzyme A. One of the hydrases is specific for the synthesis of the (3S)-isomer (enoyl coenzyme A hydrase (D)) while the other catalyzes the synthesis of the (3R)-isomer (enoyl coenzyme A hydratase (L)) |
