Multi-enzyme system for efficient bioamination of lignin-derived vanillin into vanillylamine: Enzyme structural...

Recently, there has been great interest to synthesize amines from biomass-based molecules through the biological amination with ω-transaminase under the mild conditions. In this research, pyruvate decarboxylase (PDC) was co-expressed with ω-transaminase HNILQE in a recombinant E. coli strain (HNILQE-PDC) to create a multi-enzyme pyruvate removal system. This pyruvate removal system effectively mitigated the excessive accumulation of pyruvate in the process of bioamination and significantly reduced the consumption of amine donors. The crystal structure of the ω-transaminase mutant HNILQE was resolved via X-ray crystallography at a 2.30 Å resolution. Molecular docking analysis revealed that vanillin is stabilized by a network of non-covalent interactions, including hydrogen bonding, π-cation interactions, and hydrophobic forces, particularly involving ARG128, VAL127, TRP184 and HIS55, which are critical for binding and activation. This strategy enhanced the catalytic efficiency of biocatalytic amination, achieving a productivity of 0.54 g vanillylamine per gram of vanillin. Furthermore, the bioamination strategy of multi-enzyme pyruvate removal effectively minimized by-product accumulation and demonstrated high catalytic efficiency when applied to substrates such as furfural and 5-hydroxymethylfurfural. This environmentally friendly and sustainable biocatalytic method offers significant potential for enhancing the value of biobased products by using biomass-derived platform molecules as substrates.