The axial tyrosinate Fe3+ ligand in protocatechuate 3,4-dioxygenase influences substrate binding and product release: evidence for new reaction cycle intermediates

The role of Tyr447 in catalysis was examined through site-directed mutation with Y447H. The results indicated that the disintregation of Tyr447 happens during the turnover of 3,4-dioxygenase and is critical in the substrate binding and product release processes. The removal of the Tyr447 from Fe3+ through either mutagenesis or dissociation was expedited the O2 attack and insertion processes, indicating that Tyr447 may be important in this stage of the reaction.