Industrial Biotransformations

Nitrile hydratase
Rhodococcus rhodochrous
Fig. 4.2.1.84 – 3
strain specific activity total activity
(U/mg of dry cells) (U/mL)
parent (medium A*)
0.72
0.40
parent (medium R*)
Am 3
MNNG treatment
MNNG treatment
Am 324
feeding of methacrylamide
Am 324
EC 4.2.1.84
● The third generation of industrial strains is the Rhodococcus rhodochrous J1 that produces two
kinds of nitrile-converting enzymes, the nitrilase and nitrile hydratase. The latter one was
found after optimization of fermentation medium.
● Addition of cobalt ions greatly increases nitrilase hydratase activity in comparison to Fe ions
for the Pseudomonas chlororaphis strain.
● The difference in metal-ion cofactors can be ascribed to a small number of amino acids at their
ligand-binding sites, resulting in higher stability of Rhodococcus rhodochrous J1 strain against
reducing and oxidizing agents. Although the association of 20 subunits depresses the flexibility
of the protein, it increases the stability.
● The strains forms two kinds of nitrile hydratases with different molecular weights and characteristics.
The following table compares the different enzymes and shows the advantages of
the high-molecular mass hydratase:
66
65
125
141
363
465
952
1260
* medium A: dextrin, K2HPO 4,
NaCl, MgSO and isobutyronitrile
medium R: sucrose, K HPO , KH PO , MgSO , FeSO , soybean hydrolyzate and methacrylamide
2 4 2 4 4 4
483