The power of electrified nanoconfinement for energising, controlling and observing long enzyme cascades.

Multistep enzyme-catalyzed cascade reactions are highly efficient in nature due to the confinement and concentration of the enzymes within nanocompartments. In this way, rates are exceptionally high, and loss of intermediates minimised. Similarly, extended enzyme cascades trapped and crowded within the nanoconfined environment of a porous conducting metal oxide electrode material form the basis of a powerful way to study and exploit myriad complex biocatalytic reactions and pathways. One of the confined enzymes, ferredoxin-NADP+ reductase, serves as a transducer, rapidly and reversibly recycling nicotinamide cofactors electrochemically for immediate delivery to the next enzyme along the chain, thereby making it possible to energize, control and observe extended cascade reactions driven in either direction depending on the electrode potential that is applied. Here we show as proof of concept the synthesis of aspartic acid from pyruvic acid or its reverse oxidative decarboxylation/deamination, involving five nanoconfined enzymes.