Abstract:
Immobilization of D-amino acid dehydrogenase (DAADH) by the assembly of
peptide linker was studied for biosynthesis of D-phenylalanine which is
an unnatural amino acid. Hybrid material of ZIF-8 and reduced graphene
oxide (RGO) were applied for the immobilization of DAADH
from Ureibacillus thermosphaericus . Activity of DAADH/ZIF-8/RGO
was enhanced by 1.65 folds than free enzyme. DAADH/ZIF-8/RGO remained
53.4% of its initial activity at 50 °C for 10 h. At the same time the
free enzyme was inactivated. The result indicated that the
immobilization greatly improved the thermostability of DAADH and the
stability in hyperalkaline solution. Kinetic parameters indicated that
DAADH/ZIF-8/RGO had greater affinity of phenylpyruvate as
Vm /Km of DAADH/ZIF-8/RGO was 1.27-fold
than free enzyme. After seven recycles, the activity of DAADH/ZIF-8/RGO
remained 64.3%. Furthermore, one step separation and immobilization by
ZIF-8/RGO/Ni-DAADH had 1.5-fold activity enhancement. Combination of
peptide linker and MOF immobilization, thermostability of the
dehydrogenase was significantly improved.
Keywords : D-amino acid dehydrogenase; Immobilization; Peptide
linker; Metal-organic frameworks;Reduced graphene oxide;