The hypO gene from Sinorhizobium meliloti, located within the trans-4-hydroxy-L-proline metabolic gene cluster, was first successfully expressed in the host Pseudomonas putida. Purified HypO protein functioned as a FAD-containing cis-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.
Keywords: C4DHyp, cis-4-hydroxy-D-proline; INT, p-iodonitrotetrazolium violet; L-hydroxyproline metabolism; NBT, nitroblue tetrazolium; PMS, phenazine methosulfate; Sinorhizobium meliloti; SmhypO, hypO gene from Sinorhizobium meliloti; T4DHyp, trans-4-hydroxy-D-proline; T4LHyp, trans-4-hydroxy-L-proline; cis-4-hydroxy-D-proline dehydrogenase.