Peptide bridging for cofactor channeling in fusion enzyme lowers cofactor input by two orders of magnitude

Abstract

Biocatalysis with nicotinamide adenine dinucleotide phosphate (NADP)-dependent oxidoreductases faces a challenge in improving the efficiency of the costly cofactor utilization. Although enzyme fusion can offer cofactor regeneration, the high-volume input and limited cofactor recyclability still make the enzymatic processes unsustainable. Therefore, it is of great significance to reduce cofactor input in a fusion enzyme (FuE) system, but no successful practice has been reported. Herein, we design a decapeptide bridge, RRRQRRRARR (R10), with high affinity for NADPH to construct fusion oxidoreductases (phenylacetone monooxygenase and phosphite dehydrogenase) for ester synthesis and NADP recycling. The peptide bridge enables electrostatic cofactor channeling that transports NADPH/NADP⁺ across the peptide between the enzymes’ NADP-binding pockets, so the fusion enzyme (FuE-R10) presents 2.1-folds and 2.0-folds higher conversions than mixed free enzymes and a flexible linker (GGGGSGGGGS)-fused enzyme, respectively, at NADPH/FuE of 0.1. The fusion enzyme, FuE-R5, bridged by a half-shortened linker, is proved more effective in facilitating cofactor channeling; compared to the mixed free enzymes, FuE-R5 exhibits two orders of magnitude reduction of NADPH input in ester synthesis. The work has thus demonstrated the potential of the cofactor bridging strategy in the development of sustainable cofactor-dependent cascade biocatalysis.