Aab acid (α-aminobutyric acid, 2-aminobutanowy, another short 2-ABA in English 2-aminobutyric acid, other names: homoalanina, butyryna) - an organic compound with the amino acids. Is the isomer of gamma-aminobutyric acid. It belongs to the so-called. proteinaceous α-amino acids, is not part of the protein. Exists in three stereoisomeric varieties: L-2-ABA (CAS 1492-24-6), D-2-ABA (2623-91-8) and DL-2-ABA (2835-81-6). Occurs