Reactions of the citric acid cycle

Formation of citrate

Structure of citrate synthaseopen form of the enzyme alone

Structure of citrate synthaseclosed form with bound

oxaloacetate (yellow), carboxymethyl-CoA (red)

Citrate Synthase Mechanism I.

Citrate Synthase Mechanism II.

Citrate Synthase Mechanism III.

Formation of isocitrate via cis-aconitate

Irone-sulfur center in aconitase

Isocitrate Dehydrogenase Mechanism

Isocitrate Dehydrogenase Mechanism

Step 1

Isocitrate Dehydrogenase Mechanism

Step 2

Isocitrate Dehydrogenase Mechanism

Step 3

Oxidation of -Ketoglutarate

to Succinyl-CoA and CO2

Conversion of Succinyl-CoA to Succinate

The succinyl-CoA

synthetase reaction

Step 1

Step 2

Step 3

Three-dimensional structures of Succinyl-CoA synthetase of E. coli

Oxidation of Succinate to Fumarate

Hydration of Fumarate to Malate

Oxidation of Malate to Oxaloacetate

Incorporation of the isotopic carbon (14C) of the labeled acetyl group into -ketoglutarate by the citric acid cycle

The prochiral nature of citrate

Structure of citrate

Schematic representation of citrate

X = -OH

Y = -COO-

Z = -CH2COO-

Correct complementary fit of citrate to the binding site of aconitase

Products of one turn of citric acid cycle

Biosynthetic precursors produced by an incomplete citric acid cycle in anaerobic bacteria

Role of the citric acid cycle in anabolism

Role of biotin in the reaction catalyzed by pyruvate carboxylase

Step 1

Step 2

Step 3

Step 4

Step 5

Step 6

Step 7

Biological tethers

Regulation of metabolite flow from the PDC through

the citric acid cycle

Dilution of a solution containing a noncovalent protein complex - such as one consisting of three enzymes - favors dissociation of

the complex into its constituents

Glyoxylate cycle

Electron micrograph of a germinating cucumber seed, showing a glycosome, mitochondria, and surrounding lipid bodies

Relationship between the glyoxylate and citric acid cycles

Coordinated regulation of glyoxylate and citric acid cycles