Abstract
The mechanism of asymmetric production of D-amino acids from the corresponding hydantoins by Pseudomonas sp. AJ-11220 was examined by investigating the properties of the enzymes involved in the hydrolysis of DL-5-substituted hydantoins. The enzymatic production of D-amino acids from the corresponding hydantoins by Pseudomonas sp. AJ-11220 involved the following two successive reactions; the D-isomer specific hydrolysis, i.e., the ring opening of D-5-substituted hydantoins to D-form N-carbamyl amino acids by an enzyme, D-hydantoin hydrolase (D-HYD hydrolase), followed by the D-isomer specific hydrolysis, i.e., the cleavage of N-carbamyl-D-amino acids to D-amino acids by an enzyme, N-carbamyl-D-amino acid hydrolase (o-NCA hydrolase).
L-5-Substituted hydantoins not hydrolyzed by D-HYD hydrolase were con verted" to D-form 5-substituted hydantoins through spontaneous racemization under the enzymatic reaction conditions.
It was proposed that almost all of the DL-5-substituted hydantoins were stoichiometrically and directly converted to the corresponding D-amino acids through the successive reactions of D-HYD hydrolase and o-NCA hydrolase in parrallel with the spontaneous racemization of L-5-substituted hydantoins to those of DL-form.
