H-Abu-OH (L-α-amino-n-Butyric acid) , also known as (S)-2-aminobutanoic acid, homoalanine, 2-AABA, ethylglycine, or L-butyrine, is a member of the class of compounds known as L-alpha-amino acids. H-Abu-OH is a non-proteogenic amino acid that can be found in the human kidney, in liver tissues, and in most biofluids or excreta (e.g. feces, breast milk, urine, and blood). Within the cell, H-Abu-OH is primarily located in the cytoplasm. H-Abu-OH is biosynthesized by transaminating oxobutyrate, a metabolite in isoleucine biosynthesis. As a non-proteogenic amino acid, H-Abu-OH can be used by nonribosomal peptide synthases.