A165K/N174L/T391Y
site-directed mutagenesis, the mutant shows no activity towards L-Ala, L-Lys, or L-Arg
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for D-lysine production, a two-step process for D-lysine production from L-lysine by the successive microbial racemization and asymmetric degradation with lysine racemase and decarboxylase is developed. L-lysine is rapidly racemized to give DL-lysine, and L-lysine is selectively catabolized to generate cadaverine by lysine decarboxylase. In order to obtain enantiopure D-lysine, chiral selective degradation of L-lysine from the reaction mixture of DL-lysine is necessary. Under optimal conditions, 750.7 mmol/l D-lysine is finally obtained from 1710 mmol/l L-lysine after 1 h of racemization reaction and 0.5 h of decarboxylation reaction. D-lysine yield can reach 48.8% with enantiomeric excess of 99% or more
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in an attempt to limit extracellular Lyr (while retaining the catalytic activity), amino acids 1-36 are removed from the enzyme (LyrM37) and a C-terminal KDEL ER retention motif (LyrM37-KDEL) is added
N174L
site-directed mutagenesis, inactive mutant
R173A
site-directed mutagenesis, inactive mutant
R173K
site-directed mutagenesis, inactive mutant
S394C
site-directed mutagenesis, the mutant shows 1.5fold increased activity with L-arginine compared to the wild-type enzyme
S394N
site-directed mutagenesis, the mutant shows about 2.2fold increased activity with L-arginine compared to the wild-type enzyme
S394T
site-directed mutagenesis, the mutant shows 1.8fold increased activity with L-arginine compared to the wild-type enzyme
S394Y
site-directed mutagenesis, the mutant shows 2.1fold increased activity with L-arginine compared to the wild-type enzyme
