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Thiamine pyrophosphate is a cofactor that is present in all living systems, in which it catalyzes several biochemical reactions. Thiamine pyrophosphate is synthesized in the cytosol and is required in the cytosol for the activity of transketolase and in the mitochondria for the activity of pyruvate-, oxoglutarate- and branched chain keto acid ...
It serves as a riboswitch [1] [2] that binds thiamine pyrophosphate (TPP) directly and modulates gene expression through a variety of mechanisms in archaea, bacteria and eukaryotes. [3] [4] [5] TPP is the active form of thiamine (vitamin B 1), an essential coenzyme synthesised by coupling of pyrimidine and thiazole moieties in bacteria.
[12] [13] In the body, thiamine can form derivatives; the most well-characterized of which is thiamine pyrophosphate (TPP), a coenzyme in the catabolism of sugars and amino acids. [3] The chemical structure consists of an aminopyrimidine and a thiazolium ring linked by a methylene bridge. The thiazole is substituted with methyl and hydroxyethyl ...
Pyruvate dehydrogenase complex (PDC) is a complex of three enzymes that converts pyruvate into acetyl-CoA by a process called pyruvate decarboxylation. [1] 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 .
[5] [9] [10] Mechanisms of the transformations are unknown. In Salmonella, HMP-P can be derived independently of purine biogenesis when AICAR is available. [11] [12] In algae, thiamine forms and precursors are scavenged by uptake from water of exogenous products from other organisms. In higher plants, thiamine biogenesis resembles that of bacteria.
Simplified mechanism for pyruvate dehydrogenase reaction. The TPP coenzyme is shown with abbreviated substituents. The thiamine pyrophosphate (TPP) converts to an ylide by deprotonation. The ylide attack the ketone group of pyruvate. The resulting adduct decarboxylates. The resulting 1,3-dipole reductively acetylates lipoamide-E2. [2]
Dihydrolipoyl transacetylase mechanism. Pyruvate decarboxylation requires a few cofactors in addition to the enzymes that make up the complex. The first is thiamine pyrophosphate (TPP), which is used by pyruvate dehydrogenase to oxidize pyruvate and to form a hydroxyethyl-TPP intermediate. This intermediate is taken up by dihydrolipoyl ...
H 2 O + thiamine <=> 4-amino-5-hydroxymethyl-2-methylpyrimidine + 5-(2-hydroxyethyl)-4-methylthiazole + H + [5] Produced by a wide range of plants and bacteria. In these organisms, it is mainly responsible for salvage of thiamine pyrimidine from degradation products, rather than the breakdown of thiamine. [5] In bacteria, it stays inside their ...