Mitochondrial trifunctional protein (MTP) catalyzes the latter three steps (hydration, oxidation and thiolysis) in the beta-oxidation of long-chain fatty acids. MTP consists of a hetero-octamer of four MTP-alpha and four MTP-beta subunits. The MTP-alpha subunit possesses long-chain 3-enoyl-CoA hydratase and long-chain 3-hydroxyacyl-CoA dehydrogenase activities, which catalyze the second and third steps, respectively. The MTP-beta subunit has long-chain 3-ketoacyl-CoA thiolase activity, which catalyzes the fourth step. Mitochondrial beta-oxidation is the major metabolic system to catabolize fatty acids, yielding the primary energy source for various cellular processes. (Adapted from
FBrf0217677.)
