Characterization of <i>cis</i>-4-hydroxy-D-proline dehydrogenase from <i>Sinorhizobium meliloti</i>

<p>The <i>hypO</i> gene from <i>Sinorhizobium meliloti</i>, located within the <i>trans</i>-4-hydroxy-L-proline metabolic gene cluster, was first successfully expressed in the host <i>Pseudomonas putida</i>. Purified HypO protein functioned as a FAD-containing <i>cis</i>-4-hydroxy-D-proline dehydrogenase with a homomeric structure. In contrast to other known enzymes, significant activity for D-proline was found, confirming a previously proposed potential involvement in D-proline metabolism.</p>