All subunits of human mitochondrial SDH are encoded in nuclear genome. After translation, SDHA subunit is translocated as apoprotein into the mitochondrial matrix. Subsequently, one of the first steps is covalent binding of the FAD cofactor (flavinylation). This process seems to be regulated by some of the tricarboxylic acid cycle intermediates. Specifically, succinate, isocitrate and citrate stimulate flavinylation of the SDHA. In case of eukaryotic Sdh1 (SDHA in mammals), another protein is required for process of FAD incorporation – namely Sdh5 in yeast, succinate dehydrogenase assembly factor 2 (SDHAF2) in mammal cells.