Electrochemical and spectrophotometric investigations of electron-transfer pathways in biocatalysis by PQQ-ADH

Abstract

Aiming to investigate electron-transfer pathways in biocatalysis by pyrroloquinoline-quinonedependent alcohol dehydrogenase (PQQ-ADH), the inhibition of hemes c of PQQ-ADH by CO was carried out. The inactivation kinetics was studied using a group of one- and two-electron acceptors: potassium ferricyanide (PF) and dichlorophenolindophenol (DCPIP). The inactivation constants (kin), that characterize the PQQ-ADH inactivation rate due to inhibition of hemes c were calculated. The results showed that bioelectrocatalysis by PQQ-ADH proceeds via an energetically favourable way of internal mediation; however, an alternative electron transfer switches on when the usual pathway is blocked. A mechanism of the possible electron-transfer pathways in biocatalysis by PQQ-ADH is proposed. Keywords: PQQ-dependent alcohol dehydrogenase, electron transfer, biocatalysis, inactivation kinetics