This is the C-terminal (or small) domain of tyrosine decarboxylase from Enterococcus faecalis and related species [1,2]. These are PLP-dependent decarboxylases that catalyse tyrosine decarboxylation to produce tyramine. This domain may play a regulatory role.

1: Crystal structure of tyrosine decarboxylase and identification of key residues involved in conformational swing and substrate binding. Zhu H, Xu G, Zhang K, Kong X, Han R, Zhou J, Ni Y; Sci Rep. 2016;6:27779. PMID:27292129

2: Monoamine Biosynthesis via a Noncanonical Calcium-Activatable Aromatic Amino Acid Decarboxylase in Psilocybin Mushroom. Torrens-Spence MP, Liu CT, Pluskal T, Chung YK, Weng JK; ACS Chem Biol. 2018;13:3343-3353. PMID:30484626