Transcriptionally regulated adhA gene encodes alcohol dehydrogenase required for ethanol and n-propanol utilization in Corynebacterium glutamicum R

Corynebacterium glutamicum R adhA gene encodes a homodimeric, NAD-dependent, 345 amino acid residue alcohol dehydrogenase with two zinc ions per subunit. Chromosomal inactivation of the adhA gene rendered the strain incapable of growth on either ethanol or n-propanol as the sole carbon source. RNA hybridization analysis revealed that adhA transcription was not only induced by these two substrates, but it was also subject to glucose catabolite repression. Accordingly, both induction of AdhA activity and ethanol utilization were detected only after depletion of glucose. Deletion of either or both of potential cyclic adenosine monophosphate (cAMP) receptor binding site and an inverted repeat of sequence 5'-GCAATTGATG-N (8)-CACAATTGC-3' in the promoter region of adhA strongly suggested that IR, which does not share significant similarity with other regulatory DNA elements of C. glutamicum, represents a transcriptional repressor binding site. Purified recombinant AdhA displayed the highest substrate specificities towards ethanol and n-propanol and their corresponding aldehydes.