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There is a specific mechanism for the conversion of proline to ornithine via glutamate by PutA in E. coli. In this study, C. glutamicum and derivated mutants were used to demonstrate the relationship among proline, glutamate and ornithine.
The maximum ornithine production was shown in the presence of 20 mM proline. But, glutamate has not shown any positive effect, and it suggests that the conversion of proline to ornithine via glutamate by PutA has not been available in C. glutamicum. Accordingly, it has shown to regulate the ornithine production by ornithine cyclodeaminase(Ocd) in proline-supplemented condition through the comparative analysis among wild strain, SJC8043(argR-) and SJC8064(argR- and ocd-). In addition, we found that the ornithine production is also regulated under the
transcriptional level based on the ChIP assay. Under the proline supplementation, the binding affinity of repressor ArgR was significantly reduced on the arg operon, especially the upstream of acetylglutamate kinase gene. Therefore, the results indicated that ornithine production in proline-supplemented C. glutamicumis regulated both at the decreased binding affinity of ArgR and the activated Ocd.