Figure 1. Active site cavity of PPO2.

(A) Active site of tobacco PPO2. Depicted are the investigated residues Arg⁹⁸, Leu³⁵⁶, Leu³⁷² and Phe³⁹². Phe³⁹² is shown to co-ordinate ring A of the protogen. Leu³⁵⁶ and Leu³⁷² are stacking protogen ring B from the ‘back’ and the ‘front’, and Arg⁹⁸ is supposed to co-ordinate the propionate carboxylate group of the protogen ring C. (B) VP mutants of tobacco PPO2. Asn⁶⁷ and Ser³⁷⁴ which play an important role in human VP, are depicted.