Found in all organisms, the alpha-keto acid dehydrogenase complexes have central roles in cellular metabolism and are major sites of regulation. The understanding of the organization, function and regulation of these quintessential multienzyme complexes has been greatly advanced by studies employing molecular biology and biophysical techniques. Although these enzyme systems have some features in common, their diversity in fulfilling unique organism - or tissue - specific roles is truly amazing. These systems have medical importance in areas ranging from defects in regulation (linked to...