HMGCL, also known as hydroxymethylglutaryl-CoA lyase, is a mitochondrial matrix protein that belongs to the HMG-CoA lyase family. It exists as a homodimer and participates in leucine catabolism and ketogenesis, the hepatic synthesis of ketone bodies that, during fasting, provide a major source of energy for heart, brain and kidney. More specifically, it catalyzes the final step of these processes, the cleavage of 3-hydroxy-3- methylglutaryl-CoA to acetoacetic acid and acetyl-CoA.