Identification of a transcriptional activator (ChnR) and a 6-oxohexanoate dehydrogenase (ChnE) in the cyclohexanol catabolic pathway in Acinetobactersp strain NCIMB 9871 and localization of the genes that encode them

We identified chnR, a gene encoding an AraC-XylS type of transcriptional ac tivator that regulates the expression of chnB, the structural gene for cycl ohexanone monooxygenase (CHMO) in Acinetobacter sp. strain NCIMB 9871. The gene sequence of chnE, which encodes an NADP(+)-linked 6-oxohexanoate dehyd rogenase, the enzyme catalyzing the fifth step of cyclohexanol degradation, was also determined. The gene arrangement is chnB-chnE-chnR. The predicted molecular masses of the three polypeptides were verified by radiolabeling by using the T7 expression system. Inducible expression of cloned chnB in E scherichia coli depended upon the presence of chnR. A transcriptional chnB: :lacZ fusion experiment revealed that cyclohexanone induces chnB expression in E. coli, in which a 22-fold increase in activity was observed.