Notes: 4-Hydroxyphenylpropionylglycine is a metabolite of the conditionally essential amino acid tyrosine.{51506} It is formed from tyrosine via aromatic amino acid aminotransferase, tyrosine aminotransferase, and gut microbiota, followed by glycine conjugation. 4-Hydroxyphenylpropionylglycine is also a metabolite of the phenol phloretin (Item No. 14452).{51507}