The ins and outs of vanillyl alcohol oxidase: Identification of ligand migration paths
Fig 2
Overview of the reaction cycle from p-creosol to vanillyl alcohol and vanillin catalysed by VAO.
Reaction rates at pH 7.5, 25°C are shown in the centre of the reaction cycle (data obtained from [22]). The rate-limiting step for the conversion of p-creosol to vanillyl alcohol is the decomposition of the air-stable flavin N5 substrate adduct (panel 4, marked in red). For the conversion of vanillyl alcohol to vanillin the rate-limiting step is the reduction of the flavin by the substrate (panel 7). In both reactions, the yellow flavin cofactor is rendered colorless through reduction by the substrate (occurring between panels 2 and 3 as well as 6 and 7). Molecular oxygen driven oxidation of reduced flavin (colourless) to oxidized flavin (yellow) occurs between panels 5 and 6 as well as panels 8 and 1, in the presence or absence of either vanillyl alcohol or vanillin.