<unk>  is active as a homodimer. Before addition of the pyridoxal phosphate cofactor, the apoenzyme exists in an open conformation. Upon cofactor binding, a large structural transformation occurs as the subunits pull closer and close the active site. This conformational change results in the active, closed holoenzyeme. In PLP-deficient murine models, it has been observed that dopamine levels do not significantly deviate from PLP-supplemented specimens; however, the concentration of serotonin in the deficient brain model was significant. This variable effect of PLP-deficiency indicates possible isoforms of<unk>  with differential substrate specificity for DOPA and 5-HTP. Dialysis studies also suggest that the potential isoform responsible for DOPA decarboxylation has a greater binding affinity for PLP than that of 5-HTP<unk> .
Aromatic L-amino acid decarboxylase
Phenylalanine hydroxylase
Monoamine oxidase B
Catechol-O-methyltransferase
Tyrosine hydroxylase
Dopamine beta-hydroxylase
Monoamine oxidase A
Monoamine oxidase