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an organic compound. Depending on the relative positions of the carboxyl and amino groups, the following isomers are distinguished: α-aminobutyric acid, CH3CH2CH(NH2)COOH; β-aminobutyric acid, CH3CH(NH2)CH2COOH; and γ-aminobutyric acid, NH2CH2CH2CH2COOH. The aminobutyric acids, crystalline substances with high melting points, are soluble in water and insoluble in ether. The α- and β-aminobutyric acids are optically active. The α- and γ-aminobutyric acids are widely distributed in animal and plant tissues, but β-aminobutyric acid has not been found in organisms.