Fig. 1: Schematic representation of the principle and platform pathway proposed in this study for producing diols from amino acids.

a Principle of two strategies that natural enzymes employ to overcome the thermodynamic barriers (black dashed line) for the formation of hydroxyl group from hydrocarbon by oxidation (left) and from carboxyl group by reduction (right). In the oxidative pathway, the oxidation of alkyl group is often coupled with an exergonic reaction (shown is the oxidation of α-ketoglutarate (α-KG) to succinate used in this study) (green arrow). In the reductive pathway using NAD(P)H as reducing power, ATP is normally needed as an additional energy supply (blue arrow). b The proposed pathway comprises four cascade reactions, which are successively catalyzed by amino-acid hydroxylase, l-amino acid deaminase, α-keto acid decarboxylase, and aldehyde reductase, respectively. Functional groups colored in red represent the groups modified in each step. Hydroxylation at β-position is shown only for illustration purposes. c Illustration of synthesis of diverse branched-chain diols. One hydroxyl group is formed from the amino carboxyl group via Ehrlich pathway (red dotted circles), while the other one is attached to the β-, γ-, or δ-C atom of alpha-amino acid as determined by the property of hydroxylase used.