The succinate dehydrogenase complex showing several cofactors, including flavin, iron–sulfur centers, and heme.
The "ylide form" of TPP.
A simple [Fe2S2] cluster containing two iron atoms and two sulfur atoms, coordinated by four protein cysteine residues.
TPP Mechanism
The redox reactions of nicotinamide adenine dinucleotide.
The TPP thiazolium ring can be deprotonated at C2 to become an ylid.
A full view of TPP. The arrow indicates the acidic proton.

Thiamine pyrophosphate is a cofactor that is present in all living systems, in which it catalyzes several biochemical reactions.

- Thiamine pyrophosphate

For example, the multienzyme complex pyruvate dehydrogenase at the junction of glycolysis and the citric acid cycle requires five organic cofactors and one metal ion: loosely bound thiamine pyrophosphate (TPP), covalently bound lipoamide and flavin adenine dinucleotide (FAD), cosubstrates nicotinamide adenine dinucleotide (NAD+) and coenzyme A (CoA), and a metal ion (Mg2+).

- Cofactor (biochemistry)
The succinate dehydrogenase complex showing several cofactors, including flavin, iron–sulfur centers, and heme.

4 related topics with Alpha

Overall

Skeletal formula and ball-and-stick model of the cation in thiamine

Thiamine

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Vitamin, an essential micronutrient, which cannot be made in the body.

Vitamin, an essential micronutrient, which cannot be made in the body.

Skeletal formula and ball-and-stick model of the cation in thiamine
A 3D representation of the TPP riboswitch with thiamine bound
Diamine used in the manufacture of thiamine
Takaki Kanehiro
Christiaan Eijkman
Gerrit Grijns
Umetaro Suzuki
Casimir Funk
Rudolph Peters

Within the body, the best-characterized form is thiamine pyrophosphate (TPP), also called thiamine diphosphate, a coenzyme in the catabolism of sugars and amino acids.

Transketolase

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Enzyme that is encoded by the TKT gene.

Enzyme that is encoded by the TKT gene.

Mechanism of fructose-6-phosphate to xylulose-5-phosphate in transketolase active site
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In the first reaction of the non-oxidative pentose phosphate pathway, the cofactor thiamine diphosphate accepts a 2-carbon fragment from a 5-carbon ketose (D-xylulose-5-P), then transfers this fragment to a 5-carbon aldose (D-ribose-5-P) to form a 7-carbon ketose (sedoheptulose-7-P).

The cofactor necessary for this step to occur is thiamin pyrophosphate (TPP).

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Pyruvate dehydrogenase

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Enzyme that catalyzes the reaction of pyruvate and a lipoamide to give the acetylated dihydrolipoamide and carbon dioxide.

Enzyme that catalyzes the reaction of pyruvate and a lipoamide to give the acetylated dihydrolipoamide and carbon dioxide.

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Simplified mechanism for pyruvate dehydrogenase reaction. The TPP coenzyme is shown with abbreviated substituents.
Pyruvate dehydrogenase E1 subunit of E. coli. Colors represent different chains. Structure determined by Arjunan et al. Biochemistry 2002.  Created with PyMol.
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The conversion requires the coenzyme thiamine pyrophosphate.

Mechanism of pyruvate decarboxylation.

Pyruvate decarboxylase

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Enzyme that catalyses the decarboxylation of pyruvic acid to acetaldehyde.

Enzyme that catalyses the decarboxylation of pyruvic acid to acetaldehyde.

Mechanism of pyruvate decarboxylation.

Pyruvate decarboxylase depends on cofactors thiamine pyrophosphate (TPP) and magnesium.