Effect of the half wave potential and change of some viologens on the rate of conversion of crotonic acid into butyric acid by enoate reductase

Abstract

SUMMARYThe rate of the bio-electrochemical conversion of crotonic acid into butyric acid by enoate reductase is dependent on the type of viologen used. This illustrates that the reaction between enzyme and mediator, rather than the reaction between enzyme and crotonic acid, is rate limiting. Thus for bio-electrochemical conversion of enoates into saturated chiral acids immobilization of enoate reductase is beneficial from a kinetic point of view. The highest rate constant (k'=7.0xl06 M~.s "1) was measured using mono-N-(aminopropyl) viol6gen.

Re-assessing viologens for modern bio-electrocatalysis

“…16,24,25 To date, most studies focus on the radical cation species of viologens as they are mostly soluble in aqueous systems, as compared to the fully reduced state which is typically waterinsoluble. 23,[26][27][28] Whilst some research has been done on the electron mediating potential of fully reduced viologens, 14,29 due to the insolubility of fully reduced viologens this work is limited. Altering the chemical moieties around the viologen core can greatly inuence its solubility, particularly of the fully reduced species in an aqueous medium.…”

“…Altering the chemical moieties around the viologen core can greatly influence its solubility, particularly of the fully reduced species in an aqueous medium. 29 However, this crucial aspect remains critically understudied. This untapped potential represents a new window of electrochemical opportunity for the use of viologens as NADH/NADPH replacements in bio-electrocatalysis.…”