Join the Division of Molecular and Cellular Function (MCF) for the Advances in Biosciences Seminar Series, the speaker is Dr Clare F. Megarity | Dame Kathleen Ollerenshaw Fellow | Department of Chemistry, UoM.
Hosted by Dr John Robert Davis.
Date: Tuesday, 27 May 2025
Time: 13:00-14:00
Venue: Michael Smith Lecture Theatre
Title: “Enzyme Cascades Nanoconfined, Crowded, and Electrified”
Abstract: An emergent platform called the Electrochemical Leaf (e-Leaf)1-3 provides a powerful new way to study multi-step enzyme catalysis by enabling non-electroactive enzyme cascades to be electrochemically driven and controlled. The enzymes are nanoconfined in a porous metal oxide electrode under similarly crowded conditions to those in which they function in nature and the overall cascade rate is measured as electrical current in real time.
Central to the concept is ferredoxin NADP+ reductase (FNR) – the enzyme that led to the name ‘e-Leaf’ because it converts the energised electrons produced during the photosynthetic light reactions, to hydride on NADPH, providing reducing power for the Calvin-Benson enzyme cascade of the so-called ‘dark’ reactions.
Direct electron tunnelling between the electrode and the active site flavin in FNR is key, and control of the electrode potential drives this bidirectionally to enable FNR to catalyse the interconversion of NADP+/NADPH. When an NADP(H)-dependent dehydrogenase is co-entrapped in the porous electrode, it electrically connects to FNR through recycling of the NADP(H); this step is the gateway to drive enzyme cascades with electricity transduced by FNR. Because the electron tunnelling is direct (unmediated), the cascades can be controlled by changing the direction and/or magnitude of the applied voltage (electrical potential – the thermodynamic driving force) which makes the technology inherently interactive, enabling a “dialogue” with the enzymes.
This unusual ability to engage with cascades inside a material and to sustain steady-state catalysis when the enzymes are so concentrated, has led to unexpected discoveries and examples will be highlighted, including: deracemisation by directional control of an alcohol dehydrogenase pair,4 measurement of the kinetics of extremely slow-to-bind drugs to a human enzyme driven continuously under steady state,5 a 5-enzyme cascade that incorporated CO2 into a more complex molecule, with CO2 provided in situ by co-entrapment of carbonic anhydrase in the pores,6 and discovery of a trapped intermediate state of a carboxylic acid reductase.7
A recent fundamental electrochemical study of an engineered FNR will also be discussed. By changing an active site tyrosine to serine, the flavin’s reduction potential was altered, providing insight on how biology tunes the reduction potentials of protein-bound redox cofactors.8
References
1. F. A. Armstrong*, B. Cheng, R. A. Herold, C. F. Megarity* and B. Siritanaratkul, Chemical Reviews, 2023, 123, 5421-5458.
2. B. Siritanaratkul, C. F. Megarity, R. A. Herold and F. A. Armstrong, Communications Chemistry, 2024, 7, 132.
3. C. F. Megarity, B. Siritanaratkul, R. S. Heath, L. Wan, G. Morello, S. R. FitzPatrick, R. L. Booth, A. J. Sills, A. W. Robertson, J. H. Warner, N. J. Turner and F. A. Armstrong, Angewandte Chemie International Edition, 2019, 58, 4948-4952.
4. B. Cheng, R. S. Heath, N. J. Turner, F. A. Armstrong and C. F. Megarity*, Chemical Communications, 2022, 58, 11713-11716.
5. R. A. Herold, R. Reinbold, C. F. Megarity, M. I. Abboud, C. J. Schofield and F. A. Armstrong, The Journal of Physical Chemistry Letters, 2021, 12, 6095-6101.
6. G. Morello, C. F. Megarity and F. A. Armstrong, Nature Communications, 2021, 12, 340.
7. C. F. Megarity*, T. R. I. Weald, R. S. Heath, N. J. Turner and F. A. Armstrong*, ACS Catalysis, 2022, 12, 8811-8821.
8. M. M. Doli?ska, A. J. Kirwan and C. F. Megarity*, Faraday Discussions, 2024, 252, 188-207.
Clare Megarity Biography: After initially studying Fine Art and obtaining a BA(hons) degree in painting from the Belfast School of Art, University of Ulster, Clare made an about turn and embarked on a career in science and obtained a PhD in Biochemistry from Queen’s University Belfast (2014) under the mentorship of Professor David J. Timson. Her PhD was a fundamental study on the molecular basis of negative cooperativity in a family of flavoenzymes and showed that it involved motions propagated through a specific pathway that traversed the enzyme structure connecting two active sites.
Inspired by a conference lecture by Professor Fraser Armstrong (University of Oxford) on the study of enzymes using electrochemistry, Clare joined Professor Armstrong’s laboratory in her first postdoc position in 2015 and studied terminal enzymes of photosynthetic electron-transfer chains - two hydrogenase enzymes and ferredoxin NADP+ reductase (FNR). Clare spent just over 6 years (2015-2021) in the Armstrong group to enable her to become a fully fledged enzyme electrochemist; her work on FNR contributed to the discovery of the Electrochemical Leaf.
In 2022, Clare was awarded a Dame Kathleen Ollerenshaw Fellowship from the University of Manchester to begin her independent research group. Her current research exploits electrochemistry to study fundamental enzymology and she is developing novel bio-electrochemical platforms to bring electrochemistry to enzyme systems that are currently unreachable electrochemically, with an aim to impact fundamental research in disease, antimicrobial strategy, and biosynthesis.
