Industrial Biotransformations

Tryptophan synthase
Escherichia coli
1) Reaction conditions
[1]: 0.1 M, 10.41 g · L –1 [104.1 g · mol –1 ] (initial)
[2]: 0.01 M, 1.17 g · L –1 [117.16 g · mol –1 ] (steady state)
[pyridoxal
phosphate]: > 5 · 10 –5 M (cofactor)
[3]: 0.06 M, 12.25 g · L –1 [204.23 g · mol –1 ](saturated solution)
pH: 8.0 – 9.0
T: 40 °C
medium: aqueous
reaction type: C-O bond cleavage
catalyst: suspended whole cells
enzyme: l-tryptophan synthase (l-serine hydrolyase)
strain: Escherichia coli
CAS (enzyme): [9014–52–2]
2) Remarks
● Pyridoxal phosphate is needed as cofactor.
● The enzyme works enantiospecifically for α-l-amino acid substrates of the type:
O
X OH
O
HO OH
NH2 +
NH 2
where X indicates a small nucleophilic substituent like -OH, -Cl.
N
H
1 2 3
EC 4.2.1.20
1 = L-serine
2 = indole
3 = L-tryptophan Amino GmbH
Fig. 4.2.1.20 – 1
● The established process is dedicated to the production of l-tryptophan as a pharmaceutically
active ingredient.
● The educt l-serine is separated from molasses. The best separation is performed with ion
exchange chromatography (polystyrene resin) close to the isoelectric point of serine, pH 5.7.
By concentration of the serine fraction to 35 % dry mass the main fraction of d-serine can be
separated by filtration, leaving a l-serine stock solution.
● The fed batch is pH regulated and the indole dosage is directed via on-line HPLC analysis of
the product/educt ratio.
472
E
N
H
O
OH
NH 2