4-Hydroxyphenylglycine (HPG) is a non-proteogenic amino acid found in vancomycin and related glycopeptides.

Tyrosine, a similar amino acid, differs by a methylene group (CH2) between the aromatic ring and the alpha carbon.

HPG is synthesized from prephenate, an intermediate in the shikimic acid pathway and also a precursor to tyrosine.

[3] Finally, 4-hydroxyphenylglycine transaminase (HpgT) transfers an ammonia moiety from a donor to 4-hydroxylbenzoylformate to form HPG.

[4] By doing so, the following cycle is constructed: HPG is also synthesized in Herpetosiphon aurantiacus using enzymes Haur_(1871,1887,1888).