What question did this study set out to answer?

This research aims to understand the broad substrate specificity of α-ketoacid decarboxylases (KDCs) and improve their efficiency in alcohol biosynthesis.

May 8, 2026

Mechanistic Insights into the Substrate Promiscuity of α-Ketoacid Decarboxylases for Enhanced Higher-Alcohol Biosynthesis

Puntos clave

This research aims to understand the broad substrate specificity of α-ketoacid decarboxylases (KDCs) and improve their efficiency in alcohol biosynthesis.
Crystal structures of KDC with substrates were analyzed to understand catalysis mechanisms.
The substrate-binding pocket was rationally redesigned to improve discrimination between specific substrates.
The engineered variant Q383E was tested in Escherichia coli for higher alcohol production.
The variant Q383E achieved a 16% increase in conversion efficiency.
A final titer of 27.9 g/L of 2-phenylethanol was produced during fermentation.
The structural analysis revealed key features that facilitate catalysis and broad specificity.

Resumen

α-Ketoacid decarboxylases (KDCs) are key enzymes in higher alcohol biosynthesis, but their inherent substrate promiscuity limits product selectivity and synthetic efficiency. Here, we report crystal structures of a thiamine diphosphate (ThDP)-dependent KDC in complex with multiple substrates. Structural analysis reveals an oxyanion hole─formed by a conserved HH-motif and the 4′-amino group of ThDP─that anchors the α-ketoacid moiety to facilitate catalysis. A spacious, hydrophobic substrate-binding pocket accommodates diverse substrate tails, underlying the enzyme’s broad specificity. Theoretical calculations further clarified the kinetic differences in substrate-dependent catalysis. Guided by these insights, we rationally redesigned the substrate-binding pocket to enhance discrimination between phenylpyruvate and indole-3-pyruvate. The engineered KDC variant Q383E enhanced 2-phenylethanol (2-PE) production in Escherichia coli, achieving a 16% increase in conversion efficiency and a titer of 27.9 g/L in fermentation. This work provides a mechanistic framework for tailoring KDC specificity and optimizing microbial pathways for higher alcohol biosynthesis.

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