mitochondrial fatty acid beta-oxidation multienzyme complex

Definition

Target type: cellularcomponent

A complex that includes the long-chain 3-hydroxyacyl-CoA dehydrogenase and long-chain enoyl-CoA hydratase activities in two subunits (alpha and beta), catalyzing two steps of the fatty acid beta-oxidation cycle within the mitochondrial matrix. [GOC:ma]

The mitochondrial fatty acid beta-oxidation multienzyme complex is a highly organized group of enzymes embedded within the mitochondrial matrix, responsible for the breakdown of fatty acids into acetyl-CoA, a key fuel for cellular respiration. This complex consists of four major enzyme activities: acyl-CoA dehydrogenase, enoyl-CoA hydratase, 3-hydroxyacyl-CoA dehydrogenase, and thiolase. Each enzyme performs a specific step in the four-step cycle of beta-oxidation, which repeatedly removes two-carbon units from the fatty acyl chain.

**Acyl-CoA dehydrogenase** initiates the process by catalyzing the dehydrogenation of the fatty acyl-CoA substrate, generating a trans-enoyl-CoA intermediate and reducing FAD to FADH2.

**Enoyl-CoA hydratase** adds a water molecule across the double bond of trans-enoyl-CoA, creating a 3-hydroxyacyl-CoA intermediate.

**3-hydroxyacyl-CoA dehydrogenase** oxidizes the 3-hydroxyacyl-CoA to a 3-ketoacyl-CoA, with NAD+ being reduced to NADH.

**Thiolase** cleaves the 3-ketoacyl-CoA, releasing acetyl-CoA and a shorter fatty acyl-CoA, ready to undergo another round of beta-oxidation.

The enzymes within the complex are often physically associated, though not necessarily forming a single large protein complex. This spatial proximity allows for efficient channeling of intermediates between the enzymes, minimizing diffusion losses and enhancing the overall rate of fatty acid oxidation. The complex is also tightly regulated, responding to cellular energy needs and hormonal signals, ensuring that fatty acid oxidation is appropriately balanced with other metabolic pathways.'
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Proteins (1)

Compounds (2)