Abstract
Cationic cell-wall-bound peroxidase (CWPO-C) from poplar callus is a unique peroxidase isoenzyme that has oxidizability for both synapyl alcohol and high molecule substrates unlike representative class III peroxidase such as horse radish peroxidase (HRP) and Arabidopsis thaliana peroxidase A2 (ATP A2). The simulated CWPO-C structure predicts that the entrance to the heme pocket of CWPO-C is the same size as those of HRP and ATP A2. Additionally, CWPO-C has a conserved proline (Pro)-135 corresponding to Pro-139 in the other plant peroxidases which obstruct the docking of sinapyl alcohol into heme pocket. Consequently, redox-active residues located on the protein surface were predicted to be active sites of CWPO-C.
Here, we discuss the oxidation mechanism of CWPO-C using recombinant CWPO-C protein with single amino acid substitution in which two leading candidates for the active site, tyrosine (Tyr)-74 or Tyr-177, are replaced to phenylalanine.
