Industrial Biotransformations

d-Amino acid transaminase
Bacillus sp.
EC 2.6.1.21
● The production of d-amino acids proceeds in a similar way using d-aspartase or d-glutamate
as amino-group donor.
● The α-keto acids are available by chemical or enzymatic methods. Amino acid deaminases generate
the α-keto acids from inexpensive l-amino acids. Using amino acid racemase the aminogroup
donor is also accessible from cheap racemic mixtures of amino acids. The EC-number
given above is chosen for d-alanine as precursor for the α-keto acid.
● The advantage of the process is the use of cloned strains implanted in E. coli. which are
capable of conducting all steps of synthesis using cheap racemic substrates resulting in high
yields of d-amino acids.
● The following scheme shows the coupling of the enzyme systems using l-aspargine as the
amino-group donor for the production of d-amino acids:
R
H2N COOH
D,L-amino acid
HOOC
Fig. 2.6.1.21 – 2
268
NH2
L-asparagine
+ O 2 + H2O
COOH
+
CO2
amino acid
racemase
HOOC
L-amino acid
deaminase
2-oxo-succinic acid
HOOC
O
O
pyruvic acid
COOH
NH3 + H 2O 2
HOOC
aceto lactate
synthase
NH 2
R
O COOH
COOH
D,L-asparagine
CO2
HOOC
HO
α-keto acid
O
acetolactate
+
L-amino acid
transferase
R
H2N COOH
D-amino acid
CO2
R 1
H2N COOH
D-amino acid
HO
O
acetoin