Abstract

Electron bifurcation is here described as a special case of the continuum of electron transfer reactions accessible to two-electron redox compounds with redox cooperativity. We argue that electron bifurcation is foremost an electrochemical phenomenon based on (a) strongly inverted redox potentials of the individual redox transitions, (b) a high endergonicity of the first redox transition, and (c) an escapement-type mechanism rendering completion of the first electron transfer contingent on occurrence of the second one. This mechanism is proposed to govern both the traditional quinone-based and the newly discovered flavin-based versions of electron bifurcation. Conserved and variable aspects of the spatial arrangement of electron transfer partners in flavoenzymes are assayed by comparing the presently available 3D structures. A wide sample of flavoenzymes is analyzed with respect to conserved structural modules and three major structural groups are identified which serve as basic frames for the evolutionary construction of a plethora of flavin-containing redox enzymes. We argue that flavin-based and other types of electron bifurcation are of primordial importance to free energy conversion, the quintessential foundation of life, and discuss a plausible evolutionary ancestry of the mechanism.

Highlights

  • Life fundamentally depends on the free energy ( G) provided by the electrochemical disequilibrium between reduced, electron-donating and oxidized, electron accepting environmental substrates

  • Enzyme-bound flavin, a two-electron redox compound, was proposed as the crucial redox cofactor permitting the coupling between an endergonic one-electron transfer reaction to the low potential acceptor and a exergonic one reducing the high potential acceptor (Chowdhury et al, 2016)

  • It is worth noting that electron bifurcation obviously occurs in roughly the same region of inverted redox midpoint potentials as do “both together”-type 2-electron transfer reactions such as for example in NDH-2 (Figure 1)

Read more

Summary

Introduction

Life fundamentally depends on the free energy ( G) provided by the electrochemical disequilibrium between reduced, electron-donating and oxidized, electron accepting environmental substrates (see Schoepp-Cothenet et al, 2013).

Results
Conclusion

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call

Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.