In silico and in vitro studies of the reduction of unsaturated α,β bonds of trans-2-hexenedioic acid and 6-amino-trans-2-hexenoic acid – Important steps towards biobased production of adipic acid
Fig 7
Proposed reaction mechanism of Oye1 and NemA, visualized for the reduction trans-2-hexenal.
(Residues in brackets apply to NemA.) Upon hydrogen bonding of the aldehyde to the enzyme (hashed lines) electrons from the double bond are shifted towards the catalytic residues Asn194 (His182) and His191 (His185) (dotted lines), thereby creating a partial positive charge on the β-carbon (δ+) of the substrate, which activates the double bond and makes it prone to attack. When the double bond is activated the transfer of a hydride from the flavin N5 to the β-carbon of the substrate and protonation from Tyr196 (Tyr187) can occur, resulting in hexanal as the final product. The movement of electrons involved in the hydride attack and protonation are indicated by the curved arrows.