Overview of TH isoforms. A) Overview of the four human TH isoforms with their respective amino acid length. Asterisks indicate the position of the serines that are targeted by phosphorylation. Numbers on the bottom indicate amino acids located after a splice section. B) Alignment of TH1 and TH4 for illustration of the additional amino acids, present in the different isoforms. The numbers correspond to the nucleotide numbering.