TPI1

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TPI1
Protein TPI1 PDB 1hti.png
Available structures
PDB Ortholog search: PDBe RCSB
Identifiers
Aliases TPI1, HEL-S-49, TIM, TPI, TPID, triosephosphate isomerase 1
External IDs MGI: 98797 HomoloGene: 128432 GeneCards: TPI1
Orthologs
Species Human Mouse
Entrez
Ensembl
UniProt
RefSeq (mRNA)

NM_001258026
NM_000365
NM_001159287

NM_009415

RefSeq (protein)

NP_000356
NP_001152759
NP_001244955

NP_033441.2
NP_033441

Location (UCSC) Chr 12: 6.87 – 6.87 Mb Chr 6: 124.81 – 124.81 Mb
PubMed search [1] [2]
Wikidata
View/Edit Human View/Edit Mouse

Triosephosphate isomerase is an enzyme that in humans is encoded by the TPI1 gene.

This gene encodes an enzyme, consisting of two identical proteins, which catalyzes the isomerization of glyceraldehydes 3-phosphate (G3P) and dihydroxy-acetone phosphate (DHAP) in glycolysis and gluconeogenesis. Mutations in this gene are associated with triosephosphate isomerase deficiency. Pseudogenes have been identified on chromosomes 1, 4, 6 and 7. Alternative splicing results in multiple transcript variants.[3]

Structure[edit]

Triose Phosphate Isomerase is a member of the alpha and beta (α/β) class of proteins; it is a homodimer, and each subunit contains 247 amino acids. Each TPI1 monomer contains the full set of catalytic residues, but the enzyme is only active in the oligomeric form.[4] Therefore, the enzyme must be in a dimer in order to achieve full function of the enzyme, even though it is not believed that the two active sites participate in cooperativity with each other.[5] Each subunit contains 8 exterior alpha helices surrounding 8 interior beta strands, which form a conserved structural domain called a closed alpha/beta barrel (αβ) or more specifically a TIM barrel. Characteristic of most all TIM barrel domains is the presence of the enzyme's active site in the lower loop regions created by the eight loops that connect the C-termini of the beta strands with the N-termini of the alpha helices. TIM barrel proteins also share a structurally conserved phosphate binding motif, with the phosphate group found in the substrate or cofactors.[3]

In each chain, nonpolar amino acids pointing inward from the beta strands contribute to the hydrophobic core of the structure. The alpha helices are amphipathic: their outer (water-contacting) surfaces are polar, while their inner surfaces are largely hydrophobic.

Function[edit]

TPI catalyzes the transfer of a hydrogen atom from carbon 1 to carbon 2, an intramolecular oxidation-reduction reaction. This isomerization of a ketose to an aldose proceeds through an cis-enediol(ate) intermediate. This isomerization proceeds without any cofactors and the enzyme confers a 109 rate enhancement relative to the nonenzymatic reaction involving a chemical base (acetate ion).[6] In addition to its role in glycolysis, TPI is also involved in several additional metabolic biological processes including gluconeogenesis, the pentose phosphate shunt, and fatty acid biosynthesis.

Clinical significance[edit]

Triosephosphate isomerase deficiency is a disorder characterized by a shortage of red blood cells (anemia), movement problems, increased susceptibility to infection, and muscle weakness that can affect breathing and heart function. The anemia in this condition begins in infancy. Since the anemia results from the premature breakdown of red blood cells (hemolysis), it is known as hemolytic anemia. A shortage of red blood cells to carry oxygen throughout the body leads to extreme tiredness (fatigue), pale skin (pallor), and shortness of breath. When the red cells are broken down, iron and a molecule called bilirubin are released; individuals with triosephosphate isomerase deficiency have an excess of these substances circulating in the blood. Excess bilirubin in the blood causes jaundice, which is a yellowing of the skin and the whites of the eyes. Movement problems typically become apparent by age 2 in people with triosephosphate isomerase deficiency. The movement problems are caused by impairment of motor neurons, which are specialized nerve cells in the brain and spinal cord that control muscle movement. This impairment leads to muscle weakness and wasting (atrophy) and causes the movement problems typical of triosephosphate isomerase deficiency, including involuntary muscle tensing (dystonia), tremors, and weak muscle tone (hypotonia). Affected individuals may also develop seizures. Weakness of other muscles, such as the heart (a condition known as cardiomyopathy) and the muscle that separates the abdomen from the chest cavity (the diaphragm) can also occur in triosephosphate isomerase deficiency. Diaphragm weakness can cause breathing problems and ultimately leads to respiratory failure. Individuals with triosephosphate isomerase deficiency are at increased risk of developing infections because they have poorly functioning white blood cells. These immune system cells normally recognize and attack foreign invaders, such as viruses and bacteria, to prevent infection. The most common infections in people with triosephosphate isomerase deficiency are bacterial infections of the respiratory tract. People with triosephosphate isomerase deficiency often do not survive past childhood due to respiratory failure. In a few rare cases, affected individuals without severe nerve damage or muscle weakness have lived into adulthood.[3] The deficiency is most commonly caused by mutations in TPI1, although mutations in other isoforms have been identified. A common marker for TPI deficiency is the increased accumulation of DHAP in erythrocyte extracts; this is because the defective enzyme no longer has the ability to catalyze the isomerization to GAP. The point mutation does not affect the catalysis rate, but rather, affects the assembly of the enzyme into a homodimer.[7][8]

Recent discoveries in Alzheimer's Disease research have indicated that amyloid beta peptide-induced nitro-oxidative damage promotes the nitrotyrosination of TPI in human neuroblastoma cells.[9] Nitrosylated TPI was found to be present in brain slides from double transgenic mice over-expressing human amyloid precursor protein as well as in Alzheimer's disease patients. Specifically, the nitrotyrosination occurs on Tyr164 and Tyr208 within the protein, which are near the center of catalysis; this modification correlates with reduced isomerization activity.

Interactive pathway map[edit]

Click on genes, proteins and metabolites below to link to respective articles. [§ 1]

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GlycolysisGluconeogenesis_WP534 go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to Entrez go to article go to article go to article go to article go to article go to WikiPathways go to article go to Entrez go to article
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GlycolysisGluconeogenesis_WP534 go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to article go to Entrez go to article go to article go to article go to article go to article go to WikiPathways go to article go to Entrez go to article
|{{{bSize}}}px|alt=Glycolysis and Gluconeogenesis edit]]
Glycolysis and Gluconeogenesis edit
  1. ^ The interactive pathway map can be edited at WikiPathways: "GlycolysisGluconeogenesis_WP534". 

Model organisms[edit]

Model organisms have been used in the study of TPI1 function. A conditional knockout mouse line, called Tpi1tm1a(EUCOMM)Wtsi[14][15] was generated as part of the International Knockout Mouse Consortium program — a high-throughput mutagenesis project to generate and distribute animal models of disease to interested scientists.[16][17][18]

Male and female animals underwent a standardized phenotypic screen to determine the effects of deletion.[12][19] Twenty six tests were carried out on mutant mice and three significant abnormalities were observed.[12] No homozygous mutant embryos were identified during gestation, and therefore none survived until weaning. The remaining tests were carried out on heterozygous mutant adult mice and an increased susceptibility to bacterial infection was observed in male animals.[12]

See also[edit]

References[edit]

  1. ^ "Human PubMed Reference:". 
  2. ^ "Mouse PubMed Reference:". 
  3. ^ a b c "Entrez Gene: TPI1 triosephosphate isomerase 1". 
  4. ^ Rodríguez-Almazán C, Arreola R, Rodríguez-Larrea D, Aguirre-López B, de Gómez-Puyou MT, Pérez-Montfort R, Costas M, Gómez-Puyou A, Torres-Larios A (Aug 2008). "Structural basis of human triosephosphate isomerase deficiency: mutation E104D is related to alterations of a conserved water network at the dimer interface". The Journal of Biological Chemistry. 283 (34): 23254–63. doi:10.1074/jbc.M802145200. PMID 18562316. 
  5. ^ Schnackerz KD, Gracy RW (Jul 1991). "Probing the catalytic sites of triosephosphate isomerase by 31P-NMR with reversibly and irreversibly binding substrate analogues". European Journal of Biochemistry / FEBS. 199 (1): 231–8. doi:10.1111/j.1432-1033.1991.tb16114.x. PMID 2065677. 
  6. ^ Davenport RC, Bash PA, Seaton BA, Karplus M, Petsko GA, Ringe D (Jun 1991). "Structure of the triosephosphate isomerase-phosphoglycolohydroxamate complex: an analogue of the intermediate on the reaction pathway". Biochemistry. 30 (24): 5821–6. doi:10.1021/bi00238a002. PMID 2043623. 
  7. ^ Ralser M, Heeren G, Breitenbach M, Lehrach H, Krobitsch S (20 December 2006). "Triose phosphate isomerase deficiency is caused by altered dimerization--not catalytic inactivity--of the mutant enzymes". PLOS ONE. 1: e30. doi:10.1371/journal.pone.0000030. PMC 1762313Freely accessible. PMID 17183658. 
  8. ^ Schneider AS (Mar 2000). "Triosephosphate isomerase deficiency: historical perspectives and molecular aspects". Baillière's Best Practice & Research. Clinical Haematology. 13 (1): 119–40. doi:10.1053/beha.2000.0061. PMID 10916682. 
  9. ^ Guix FX, Ill-Raga G, Bravo R, Nakaya T, de Fabritiis G, Coma M, Miscione GP, Villà-Freixa J, Suzuki T, Fernàndez-Busquets X, Valverde MA, de Strooper B, Muñoz FJ (May 2009). "Amyloid-dependent triosephosphate isomerase nitrotyrosination induces glycation and tau fibrillation". Brain. 132 (Pt 5): 1335–45. doi:10.1093/brain/awp023. PMID 19251756. 
  10. ^ "Salmonella infection data for Tpi1". Wellcome Trust Sanger Institute. 
  11. ^ "Citrobacter infection data for Tpi1". Wellcome Trust Sanger Institute. 
  12. ^ a b c d Gerdin AK (2010). "The Sanger Mouse Genetics Programme: High throughput characterisation of knockout mice". Acta Ophthalmologica. 88: 925–7. doi:10.1111/j.1755-3768.2010.4142.x. 
  13. ^ Mouse Resources Portal, Wellcome Trust Sanger Institute.
  14. ^ "International Knockout Mouse Consortium". 
  15. ^ "Mouse Genome Informatics". 
  16. ^ Skarnes WC, Rosen B, West AP, Koutsourakis M, Bushell W, Iyer V, Mujica AO, Thomas M, Harrow J, Cox T, Jackson D, Severin J, Biggs P, Fu J, Nefedov M, de Jong PJ, Stewart AF, Bradley A (Jun 2011). "A conditional knockout resource for the genome-wide study of mouse gene function". Nature. 474 (7351): 337–42. doi:10.1038/nature10163. PMC 3572410Freely accessible. PMID 21677750. 
  17. ^ Dolgin E (Jun 2011). "Mouse library set to be knockout". Nature. 474 (7351): 262–3. doi:10.1038/474262a. PMID 21677718. 
  18. ^ Collins FS, Rossant J, Wurst W (Jan 2007). "A mouse for all reasons". Cell. 128 (1): 9–13. doi:10.1016/j.cell.2006.12.018. PMID 17218247. 
  19. ^ van der Weyden L, White JK, Adams DJ, Logan DW (2011). "The mouse genetics toolkit: revealing function and mechanism". Genome Biology. 12 (6): 224. doi:10.1186/gb-2011-12-6-224. PMC 3218837Freely accessible. PMID 21722353. 

Further reading[edit]