Mechanism of Stereospecific Conversion of dl-5-Substituted Hydantoins to the Corresponding l-Amino Acids by Pseudomonas sp. Strain NS671

Abstract

The mechanism of stereospecific conversion of dl-5-substituted hydantoins to the corresponding l-amino acids by Pseudomonas sp. strain NS671 was studied. The results indicated that the hydantoinase catalyzed the hydrolysis reaction of both d-and l-5-(2-methylthioethyl)hydantoin, and that the hydrolysis of the l-enantiomer proceeded preferentially compared with that of the d-enantiomer. On the basis of these findings, the mechanism was speculated to be as follows: dl-5-substituted hydantoins are converted exclusively to the l-forms of the corresponding N-carbamylamino acids by the hydantoinase in combination with hydantoin racemase. The N-carbamyl-l-amino acids are then converted to l-amino acids by N-carbamyl-l-amino acid amidohydrolase.

Key words:

• l-amino acid production
• hydantoinase
• Pseudomonas sp. strain NS671
• 5-substituted hydantoin