Formaldehyde dehydrogenase SzFaldDH: an indispensable bridge for relaying CO2 bioactivation and conversion†

Abstract

Formaldehyde dehydrogenases (FaldDHs) are becoming attractive biocatalysts as an indispensable bridge for relaying CO₂ bioactivation and conversion by multi-enzyme cascade reactions (CO₂ → HCOOH → HCHO → C_n) in a green process. This study has discovered four novel FaldDHs using the effective bioinformatics tool Peptide Pattern Recognition (PPR), among which SzFaldDH was shown to have outstanding reducing activity 10-fold greater than the commercial PFaldDH. This new FaldDH achieved the highest catalytic efficiency among all free enzyme systems of CO₂ → HCHO at 0.496 μmol g_enzyme⁻¹ min⁻¹. The outstanding reducing capability was attributed to the enlarged substrate tunnel achieved by residue at the entrance and an extra loop, making it easier for the combination with the substrates. The Quantum Mechanics and Molecular Dynamic calculations revealed the facilitation of hydrogen transfer between formate and NADH as well as protonation of carbonyl oxygen also contributed to the high reducing activity. This discovery provided a novel effective biocatalyst for further promoting the conversion and utilization of CO₂.