Optimization of the enzymatic synthesis of D-p-hydroxyphenylglycine from DL-5-substituted hydantoin using D-hydantoinase and N-carbamoylase
Geun-Joong Kim and Hak-Sung Kim
D-hydantoinase and N-carbamoylase possessed in a bacterium Agrobacterium sp I-671 were partially purified to about 90% purity on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and biochemical properties were characterized. The N-carbamoylase was found to be severly inhibited by ammonium ions coproduced with D-p-hydroxyphenylglycine(D-HPG). For the enhancement of conversion yield, adsorptive removal of ammonium ions from the reaction mixture was attempted, and the conversion yield of D-HPG sigificantly increased by the addition of specific adsorbents for ammonium ions. To determine the optimal ratio of D-hydantoinase to N-carbamoylase which minimizes the accumulation of intermediate (N-carbamoyl-D-p-hydroxyphenylglycine) in the direct enzymatic production of D-HPG, a sequential reaction was numerically simulated. Simulation results coincided well Àç¼Ò experimental data, and the optimal ratio between D-hydantoinase and N-carbamoylase was found to be about 1:3 on a weight basis.