| 초록 |
D-2-hydroxy acid dehydrogenases (D-2-HADHs), including D-lactate dehydrogenases (D-LDHs), reduce 2-oxo acids into corresponding D-2-hydroxy acids, yet they have presented lower activities toward 2-oxo acids with bulky C3 functional groups. Four putative D-2-HADHs from lactic acid bacteria have been selected based on their amino acid sequences and investigated for catalytic activities on the reduction of phenylpyruvate (PPA) to D-3-phenyllactic acid (PLA). The enzyme from Pediococcus claussenii has shown the highest catalytic efficiency and substrate selectivity for the PPA over pyruvate. Structural and mutational studies of the enzyme have revealed that it belongs to the D-LDH family, and phenylalanine at the position 51 stabilized PPA binding. The structural information obtained has also been applied to mutate the D-LDH from Pediococcus acidilactici, whose wild-type has a tyrosine at the same position. The resulting P. acidilactici D-LDH Y51F mutant, as well as Y51L and Y51M, had over 138-fold increase in catalytic efficiency than the wild-type. Activities for other substrates such as 2-oxobutyrate and 3-methyl-2-oxobutyrate, have also increased in the Y51F mutant.
|
