Stereoselective hydrolysis of aryl-substituted dihydropyrimidines by hydantoinases.

In this study, we investigated the possibility of using a modified hydantoinase process for the production of optically pure β-amino acids. Two aryl-substituted dihydropyrimidines D,L-6-phenyl-5,6-dihydrouracil (PheDU) and para-chloro-D,L-6-phenyl-5,6-dihydrouracil (pClPheDU) were synthesized. Hydrolysis of these novel substrates to the corresponding N-carbamoyl-β-amino acids by three recombinant D-hydantoinases and several bacterial strains was tested. All applied recombinant D-hydantoinases and eight bacterial isolates catalyzed the conversion of PheDU to N-carbamoyl-β-phenylalanine (NCβPhe). Some of these biocatalysts showed an enantioselectivity for either the D- or the L-PheDU enantiomer. The second dihydropyrimidinase substrate pClPheDU was hydrolyzed by all three recombinant D-hydantoinases and six of the wild-type strains. To our knowledge, this is the first dihydropyrimidinase activity reported with this aryl-substituted dihydropyrimidine. For selected biocatalysts, hydantoinase activity towards aryl-substituted hydantoins was demonstrated as well. However, none of the bacterial strains tested so far exhibited any carbamoylase activity towards NCβPhe.