The Citric Acid Cycle

The citric acid cycle is also called the tricarboxylic acid (TCA) cycle and the Krebs cycle. It is the final common catabolic pathway for the oxidation of fuel molecules. Two carbons enter the citric acid cycle as acetyl CoA and two carbons leave as CO₂. In the course of the cycle, four oxidation-reduction reactions take place to yield reduction potential in the form of three molecules of NADH and one molecule of FADH₂. A high energy phosphate bond (GTP) is also formed.

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Pyruvate Dehydrogenase Complex
Structure of the thiamin diphosphate dependent enzyme pyruvate decarboxylase
(the E₁ part of the complex)
(1pyd.pdb)

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Source: brewer's yeast Saccharomyces cerevisiae uvarum strain
Authors: F. Dyda, W. Furey, S. Swaminathan, M. Sax, B. Farrenkopf, F. Jordan
Reference: Biochemistry, 1993, 32, 6165.

Pyruvate Dehydrogenase Complex
The lipoyl E₂ domain of complex which serves as an acyltransferase.
(1iyu.pdb)

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Source: Azotobacter vinelandii
Authors: A. Berg, J. Vervoort, A. De Kok
Reference: J. Mol. Biol., 1996, 261, 432.

Citrate Synthase
Citrate Synthase (E.C.4.1.3.7) complexed with oxaloacetate and amidocarboxymethyldethia coenzyme A.
(1csh.pdb)

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Source: Chicken (Gallus gallus) heart muscle
Authors: K. C. Usher, S. J. Remington, M. Karpusas, B. Branchaud, S. J. Remington
Reference: Biochemistry, 1990, 29, 2213.

Aconitase
Aconitase (E.C.4.2.1.3) in the activated (4Fe-4S) cluster form.
(6acn.pdb)

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Source: Pig heart
Authors:A. H. Robbins, C. D. Stout
Reference: Proc. Nat. Acad. Sci., 1989, 86, 3639.

Isocitrate Dehydrogenase
Isocitrate Dehydrogenase (E.C.1.1.1.42) with NADP⁺
(9icd.pdb)

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Source: Escherichia coli
Authors: J. H. Hurley, A. M. Dean, D. E. Koshland Jr, R. M. Stroud
Reference: Biochemistry, 1991, 30, 8671.

Succinyl-CoA Synthetase
Succinyl-CoA Synthetase (E.C.6.2.1.5) with coenzyme A
(1scu.pdb)

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Source: Escherichia Coli Strain: Cr63
Authors: W. T. Wolodko, M. E. Fraser, M. N. G. James, W. A. Bridger
Reference: J. Biol. Chem., 1984, 249, 5316.

Fumarase
Fumarase with bound malate.
(1fup.pdb)

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Source: Escherichia coli
Authors: T. M. Weaver, D. G. Levitt, M. I. Donnelly, P. P. Stevens, L. J. Banaszak
Reference: Nat. Struct. Biol., 1995, 2, 654.

Malate Dehydrogenase
Malate Dehydrogenase (E.C.1.1.1.37) a complex of the apoenzyme and citrate
(2cmd.pdb)

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Source: Escherichia coli
Authors: M. D. Hall, D. G. Levitt, L. J. Banaszak
Reference: J. Mol. Biol., 1992, 226, 867.

Citations for the Protein Data Bank

The PDB files on this page were obtained from the Protein Data Bank, and were created by the authors listed above. The Protein Data Bank, maintained by the Research Collaboratory for Structural Bioinformatics is an archival database of the three-dimensional structures of biological macromolecules such as proteins, nucleic acids and carbohydrates. The stuctures are derived from experimental work such as X-ray diffraction studies and NMR investigations.

The contents of PDB are in the public domain, but it is expected that the authors of an entry as well as the PDB be properly cited whenever their work is referred.

The following is the current citation for the PDB:

Nucleic Acids Research

2000

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