Cyanide sensitivity in direct electron transfer-type bioelectrocatalysis by membrane-bound alcohol dehydrogenase from Gluconobacter oxydans.

An overexpression system of membrane-bound alcohol dehydrogenase (ADH) from Gluconobacter oxydans was constructed to examine its bioelectrocatalytic characteristics. The effects of cyanide (CN-) addition on the kinetics of direct electron transfer (DET)-type bioelectrocatalysis by ADH were analyzed. CN- enhanced the bioelectrocatalytic activity, while the catalytic activity in the solution remained unchanged, even in the presence of CN-. Electrochemical methods and electron spin resonance spectroscopy showed the detailed electron transfer pathway in the DET-type bioelectrocatalysis by ADH. Briefly, ADH is suggested to communicate with an electrode via a CN--insensitive and H+-sensitive heme c in DET. These characteristics of ADH with respect to CN- suggest the involvement of ADH in CN--insensitive respiration in G. oxydans.