fenylthiohydantoin

Phenylthiohydantoin, often abbreviated as PTH, is a derivative of the amino acid and is formed during the Edman degradation process. This process is a method used to determine the sequence of amino acids in a protein or peptide. In Edman degradation, the N-terminal amino acid of a protein is reacted with phenyl isothiocyanate (PITC) under alkaline conditions. This reaction forms a phenylthiocarbamoyl (PTC) adduct. This PTC-adduct is then treated with a strong acid, which cleaves the N-terminal amino acid as a substituted phenylthiohydantoin. The phenylthiohydantoin derivative can then be identified by techniques such as chromatography. The remaining peptide is shortened by one amino acid and can be subjected to further cycles of Edman degradation to reveal the entire amino acid sequence. PTH derivatives are relatively stable and can be readily detected and quantified, making them suitable for automated sequencing. The identity of the PTH-amino acid corresponds to the identity of the N-terminal amino acid at each step of the degradation.