Direct electron transfer-type bioelectrocatalysis by membrane-bound aldehyde dehydrogenase from Gluconobacter oxydans and cyanide effects on its bioelectrocatalytic properties.

• Membrane-bound aldehyde dehydrogenase (AlDH) was examined as a bioelectrocatalyst. • AlDH enabled the direct electron transfer (DET)-type acetaldehyde oxidation. • The bioelectrocatalysis of AlDH was kinetically and thermodynamically analyzed. • Cyanide (CN−) inhibition proved the involvement of hemes c in DET by AlDH. • CN−-coordinated AlDH catalyzed the DET-type acetate reduction under acidic conditions. The bioelectrocatalytic properties of membrane-bound aldehyde dehydrogenase (AlDH) from Gluconobacter oxydans NBRC12528 were evaluated. AlDH exhibited direct electron transfer (DET)-type bioelectrocatalytic activity for acetaldehyde oxidation at several kinds of electrodes. The kinetic and thermodynamic parameters for bioelectrocatalytic acetaldehyde oxidation were estimated based on the partially random orientation model. Moreover, at the multi-walled carbon nanotube-modified electrode, the coordination of CN− to AlDH switched the direction of the DET-type bioelectrocatalysis to acetate reduction under acidic conditions. These phenomena were discussed from a thermodynamic viewpoint. [ABSTRACT FROM AUTHOR]