HADHA also known as trifunctional enzyme subunit alpha, ECHA is a crucial 763 amino acid component of the mitochondrial trifunctional protein complex, which plays a vital role in the final three steps of mitochondrial beta-oxidation of long-chain fatty acids. This complex is composed of four alpha (HADHA) and four beta (HADHB) subunits, with the alpha subunit specifically responsible for catalyzing the 3-hydroxyacyl-CoA dehydrogenase and enoyl-CoA hydratase activities. Proper functioning of HADHA is essential for efficient fatty acid metabolism, as deficiencies in HADHA can lead to severe metabolic disorders such as long-chain 3-hydroxyacyl-coenzyme A dehydrogenase deficiency and mitochondrial trifunctional protein deficiency.