Deracemisation and stereoinversion by a nanoconfined bidirectional enzyme cascade: dual control by electrochemistry and selective metal ion activation.

The unique ability of the 'electrochemical leaf' (e-Leaf) to drive and control nanoconfined enzyme cascades bidirectionally, while directly monitoring their rate in real-time as electrical current, is exploited to achieve deracemisation and stereoinversion of secondary alcohols using a single electrode in one pot. Two alcohol dehydrogenase enzymes with opposing enantioselectivities, from Thermoanaerobacter ethanolicus (selective for S ) and Lactobacillus kefir (selective for R ) are driven bidirectionally via coupling to the fast and quasi-reversible interconversion of NADP + /NADPH catalysed by ferredoxin NADP + reductase - all enzymes being co-entrapped in a nanoporous indium tin oxide electrode. Activity of the Lactobacillus kefir enzyme depends on the binding of a non-catalytic Mg 2+ , allowing it to be switched off after an oxidative half-cycle, by adding EDTA - the S -selective enzyme, with a tightly-bound Zn 2+ , remaining fully active. Racemate → S or R → S conversions are thus achieved in high yield with unprecedented ease.