In my search for Glu decarboxylation to make GABA to be transformed to GHB I noticed this paper. I'd suspect it applies to other aromatic amino acids and not just Phe and I hadn't seen it mentioned on the Hive.
Oxidation studies. Part II: Kinetics of the oxidative decarboxylation of some amino acids by peroxydisulfate catalyzed by silver ions.
The kinetics of oxidative decarboxylation of glycine, glutamic acid, serine, proline, aspartic acid, hydroxyproline, and phenylalanine by S2O82- catalyzed by Ag+ followed 2 distinct rate laws, [S2O82-][Ag+] at high amino acid concn. and [S2O82-][Ag+]1/2[amino acid]1/2 at low amino acid concn.
The journal is Z.Phys.Chem. 1975, 256(6):880-4 and luckily it's in English for anyone who wants to follow it up.