Rv2607 from <em>Mycobacterium tuberculosis</em> Is a Pyridoxine 5′-Phosphate Oxidase with Unusual Substrate Specificity

Despite intensive effort, the majority of the annotated Mycobacterium tuberculosis genome consists of genes encoding proteins of unknown or poorly understood function. For example, there are seven conserved hypothetical proteins annotated as homologs of pyridoxine 5′-phosphate oxidase (PNPOx), an enzyme that oxidizes pyridoxine 5′-phosphate (PNP) or pyridoxamine 5′-phosphate (PMP) to form pyridoxal 5′-phosphate (PLP). We have characterized the function of Rv2607 from Mycobacterium tuberculosis H37Rv and shown that it encodes a PNPOx that oxidizes PNP to PLP. The kcat and KM for this reaction were 0.01 s−1 and 360 µM, respectively. Unlike many PNPOx enzymes, Rv2607 does not recognize PMP as a substrate.