Peroxiomal multifunctional enzyme type 2 (MFE-2) is a three part enzyme used in beta oxidation of very-long-chain fatty acids. The enzyme works the second and third steps in the peroxisomal beta oxidation. The three parts of the enzyme include (3R)-hydroxyacyl-CoA dehydrogenase ((3R)-dehydrogenase), sterol carrier protein 2-like units (SCP-2L), and 2-enoyl-CoA hydratase (hydratase 2). MFE-2 is a two-domain structure with a C-domain complete hot-dog fold around the active site, and a N-domain fold housing the cavity for the aliphatic acyl part of the substrate molecule. MFE-2 is essential in the breakdown of very-long-chain fatty acids, as well as bile acid synthesis.
Function
The (3R)-dehydrogenase unit belongs to the short-chain alcohol dehydrogenase/reductase (SDR) with a typical Rossman fold. Unlike most other enzymes in the SDR, the (3R)-dehydrogenase has an extra C-terminal which helps to form the active site cavity.
The hydratase 2 enzyme is used by the enzyme to catalyze the (R)-specific hydration of 2-enoyl-CoA thioesters, and are part of the hydratase/isomerase family. This family of enzyme molecules is used to hydrate the straight-chain fatty-enoyl-CoAs from C8 to C12 with high efficiency. The catalytic activity of this molecule is housed by the active site residues of Ala613-Lys614-Thr615
Disease
Relevance
Structural highlights
The Rossman fold found in the (3R)-dehydrogenase has a G-X-X-X-G-X-G amino acid motif, this allows for the co-factor binding with the Ser-Tyr-Lys. The SCP-2L unit consists of a five-stranded beta sheet covered on one side by five alpha helices. When the substrate binds in the SCP-2L, it structurally changes the C-terminal alpha helices. This causes the peroxisomal targeting signal Ala-Lys-Leu, to become solvent-exposed to strengthen the idea of ligand assisted targeting. The hydratase 2 unit is a homodimer with a two-domain subunit structure whit a hot dog fold. The size of the hydratase 2 portion of the enzyme was found to be 31.5 kDa upon SDS-Page analysis of rat liver peroxisomes.
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