Biochemical Characterization of Hydantoin Racemase Enzymes

Although on the whole the hydantoin racemases have shown high thermal stability, with optimal activity at 55 °C (Table 12.2), the optimal temperatures for the ones from Pseudomonas and Sinorhizobium decrease to 45 and 40 °C, respectively. However, the optimal pH is higher than 8, except for both hydantoin racemases from Agrobacterium. This low alkaline pH avoids chemical racemization. Consequently, the racemization of the d- or L-5-monosubstituted hydantoins in an industrial process will only occur enzymatically. 

The activity of the purified hydantoin racemase enzymes has been assayed in the presence of different metal ions, the chelating agent EDTA, and the reducing compound dithiothreitol, in order to study whether they are metaUoenzymes. Most 

Strain System chirality Molecular weight of Monomers (kDa) Number of subunits Optimal pH Optimal temperature (°q 

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