Acyl-CoA dehydrogenase, C-2 to C-3 short chain is an enzyme that in humans is encoded by the ACADS gene. This gene encodes a tetrameric mitochondrial flavoprotein, which is a member of the acyl-CoA dehydrogenase family. This enzyme catalyzes the initial step of the mitochondrial fatty acid beta-oxidation pathway. The ACADS gene associated with short-chain acyl-coenzyme A dehydrogenase deficiency. The SCAD enzyme catalyzes the first part of fatty acid beta-oxidation by forming a C2-C3 trans-double bond in the fatty acid through dehydrogenation of the flavoenzyme. SCAD is specific to short-chain fatty acids, between C2 and C3-acylCoA. The final result of beta-oxidation is acetyl-CoA. When there are defects that result in SCAD being misfolded, there is an increased production of reactive oxygen species (ROS); the increased ROS forces the mitochondria to undergo fission, and the mitochondrial reticulum takes on a grain-like structure. Mutations of the ACADS gene are associated with deficiency of the short-chain acyl-coenzyme A dehydrogenase protein (SCADD); this is also known as butyryl-CoA dehydrogenase deficiency. The ACADS gene has also been implicated in delaying the onset of Prader-Willi Syndrome, which is characterized by hypotonia, growth failure, and neurodevelopmental delays in the first years of life, and hyperphagia and obesity much later. In Genome Wide Association Studies (GWAS), SCAD has been associated with a reduced amount of insulin release shown by an oral glucose tolerance test, or OGTT.