Figure 6. PAL reaction mechanism.
A mechanism for PAL is proposed on the basis of structural and biochemical data. After substrate binding to the active site through coordination of the substrate a-hydoxyl group to the Zn(II) ion, the Tyr654 (as phenolate) deprotonates the substrate α-OH, triggering Cα-N bond cleavage and formation of the amidated peptide and glyoxylate.