Hydroxyacid Oxidase 1 (HAO1) is an enzyme that belongs to the FMN-Dependent α-Hydroxy Acid Dehydrogenase family. HAO1 contains 1 FMN Hydroxy Ccid Dehydrogenase domain. HAO1 is expressed primarily in the liver and pancreas. This protein has 2-Hydroxyacid Oxidase activity. Most HAO1 is active on the 2-Carbon substrate Glycolate, but it can also be active on 2-Hydroxy fatty acids, with higher activity towards 2-Hydroxy Palmitate and 2-Hydroxy Octanoate.