Chemistry Reference
In-Depth Information
NH
2
Me
CO
2
H
Me
Me
HCO
2
NAD
(
S
)-
147
>99% ee
Leucine
dehydrogenase,
ammonia
Formate
dehydrogenase
O
Me
CO
2
H
CO
2
NADH
Me
Me
146
Scheme 6.62.
NH
2
HO
CO
2
H
D-glucose
NAD
(
S
)-
149
92% yield
>99% ee
Glutamate
dehydrogenase,
ammonia
Glucose
dehydrogenase
O
D-glucono-
lactone
HO
CO
2
H
NADH
148
(100 g/L
substrate input)
Scheme 6.63.
However, in spite of high effi ciency, the need for isolated, costly enzymes as well as
the need for the addition of expensive cofactor NAD
+
(although used in catalytic
amounts) is disadvantageous. Thus, efforts have been made to address these issues. The
direct use of a whole-cell catalyst, containing both an amino acid dehydrogenase and
FDH in overexpressed form, has been reported by Esaki et al. in their pioneer work for
several amino acids [257]. The desired amino acids were obtained with high conversion
and excellent enantioselectivity. For example, L-leucine, L-valine, and L-norvaline were
synthesized with a recombinant whole-cell catalyst overexpressing a LeuDH with con-
versions of 95-97% and enantioselectivities of >99% ee. When using a whole-cell cata-
lyst bearing a phenylalanine dehydrogenase as amino acid dehydrogenase, L-tyrosine
(92% conversion) and L-phenylalanine (95% conversion) were formed in enantiomeri-
cally pure form.
