Figure 10.

Preliminary modeling with SwissPdbViewer of the catalytic site of Pg DODA (A) and the moss P. patens DODA homolog (B) based on the three-dimensional structure 1B4U of Sphingomonas sp. LigAB. Referring to Pg DODA sequence, catalytic His-177 is conserved (blue), whereas the three following residues conserved in betalain plants Pro-178-Ser-179-Asp-180 are replaced in all non-betalain plants by Asn-178-Leu-179-Arg-180, which reduce clearly the access to the catalytic site represented by the three conserved His linking the iron cofactor (red) and the two conserved His making hydrogen bonds with the substrate (blue). Pro-178-Ser-179-Asp-180 and Thr-182-Pro-183 are conserved only in betalain plants potentially participating to the substrate recognition.