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Concept
Pyruvate dehydrogenase complex
Summary
Pyruvate dehydrogenase complex (PDC) is a complex of three enzymes that converts pyruvate into acetyl-CoA by a process called pyruvate decarboxylation. Acetyl-CoA may then be used in the citric acid cycle to carry out cellular respiration, and this complex links the glycolysis metabolic pathway to the citric acid cycle. Pyruvate decarboxylation is also known as the "pyruvate dehydrogenase reaction" because it also involves the oxidation of pyruvate.
This multi-enzyme complex is related structurally and functionally to the oxoglutarate dehydrogenase and branched-chain oxo-acid dehydrogenase multi-enzyme complexes.
The reaction catalysed by pyruvate dehydrogenase complex is:
The E1 subunit, called the pyruvate dehydrogenase subunit, has a structure that consists of two chains (an “ɑ” and “ꞵ” chain). A magnesium ion forms a 4-coordinate complex with three, polar amino acid residues (Asp, Asn, and Tyr) located on the alpha chain, and the thiamine diphosphate (TPP) cofactor directly involved in decarboxylation of the pyruvate.
The E2 subunit, or dihydrolipoyl acetyltransferase, for both prokaryotes and eukaryotes, is generally composed of three domains. The N-terminal domain (the lipoyl domain), consists of 1–3 lipoyl groups of approximately 80 amino acids each. The peripheral subunit binding domain (PSBD), serves as a selective binding site for other domains of the E1 and E3 subunits. Finally, the C-terminal (catalytic) domain catalyzes the transfer of acetyl groups and acetyl-CoA synthesis.
The E3 subunit, called the dihydrolipoyl dehydrogenase enzyme, is characterized as a homodimer protein wherein two cysteine residues, engaged in disulfide bonding, and the FAD cofactor in the active site facilitate its main purpose as an oxidizing catalyst. One example of E3 structure, found in Pseudomonas putida, is formed such that each individual homodimer subunit contains two binding domains responsible for FAD binding and NAD binding, as well as a central domain and an interface domain.
Official source
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