Substrate binding pocket predicted with the autodock result. A. PnpE is shown in surface model in yellow. NAD is depicted in green sticks and γ-hydroxymuconic semialdehyde is shown in red sticks. B. PnpE is shown in green ribbon model. There are nine amino acids interact with the substrate: C281, E247, F150, I282, F154, H275, F447, W157 and N149.