The ahpD gene of Corynebacterium glutamicum plays an important role in hydrogen peroxide-induced oxidative stress...

In this study, we analysed the ahpD gene from Corynebacterium glutamicum, which may function in a H2O2-mediated stress responses. Cells overexpressing C. glutamicum ahpD (P180-ahpD) showed increased sensitivity to H2O2 when exposed to the latter in concentrations of 8 mM or greater while showing reduced expression of katA, which encodes catalase. On the other hand, cells that lack ahpD (ΔahpD) displayed increased sensitivity when exposed to low levels of H2O2 while showing katA transcription that was comparable to the level in the wild-type strain. Accordingly, transcription of ahpD and katA was stimulated by low and high concentration of H2O2, respectively. Further, the NAD+/NADH ratio was severely reduced in the ΔahpD (3.03) and P180-ahpD (0.47) strains as compared with that in the wild-type (4.55) strain. Transcriptional analysis indicated that ahpD and upstream genes such as cg2675, cg2676, cg2677 and cg2678, which were annotated as ABC-type transporter, were organized into an operon. Collectively, these findings indicate that C. glutamicum possesses bi-level defence pathways against hydrogen peroxide, involving katA and ahpD. Further, ahpD, along with cg2675-cg2678 genes, may play a novel role in cellular activities against oxidative stress.