Pyruvate dehydrogenase (lipoamide) beta

Last updated
PDHB
PDB 3exi EBI.png
Available structures
PDB Ortholog search: PDBe RCSB
Identifiers
Aliases PDHB , PDHBD, PDHE1-B, PHE1B, Pyruvate dehydrogenase (lipoamide) beta, PDHE1B, pyruvate dehydrogenase E1 beta subunit, pyruvate dehydrogenase E1 subunit beta
External IDs OMIM: 179060; MGI: 1915513; HomoloGene: 712; GeneCards: PDHB; OMA:PDHB - orthologs
Orthologs
SpeciesHumanMouse
Entrez
Ensembl
UniProt
RefSeq (mRNA)

NM_000925
NM_001173468
NM_001315536

NM_024221

RefSeq (protein)

NP_000916
NP_001166939
NP_001302465

NP_077183

Location (UCSC) Chr 3: 58.43 – 58.43 Mb Chr 14: 14.3 – 14.3 Mb
PubMed search [3] [4]
Wikidata
View/Edit Human View/Edit Mouse

Pyruvate dehydrogenase (lipoamide) beta, also known as pyruvate dehydrogenase E1 component subunit beta, mitochondrial or PDHE1-B is an enzyme that in humans is encoded by the PDHB gene. [5] [6] The pyruvate dehydrogenase (PDH) complex is a nuclear-encoded mitochondrial multienzyme complex that catalyzes the overall conversion of pyruvate to acetyl-CoA and CO2, and provides the primary link between glycolysis and the tricarboxylic acid (TCA) cycle. The PDH complex is composed of multiple copies of three enzymatic components: pyruvate dehydrogenase (E1), dihydrolipoamide acetyltransferase (E2) and lipoamide dehydrogenase (E3). The E1 enzyme is a heterotetramer of two alpha and two beta subunits. This gene encodes the E1 beta subunit. Mutations in this gene are associated with pyruvate dehydrogenase E1-beta deficiency. [5]

Contents

Structure

The PDH genes that comprise the E1 subunit are 1.36 kilobases long (alpha) and 1.69 kb long (beta). [7] The PDHB gene has a total of 10 exons and 9 introns. All intron-exon splice junctions follow the standard GT/AG rule. There was an Alu family found in introns 2 and 8. The 5' flanking region gene contains a "CAAT" consensus promoter sequence but no "TATA" sequence. The transcription start site is an adenine residue located 132 bases upstream from the initiation codon in exon 1. [8] The mRNA species that results from transcription of PDHB has been experimentally determined, via Northern blotting, to be 1.6 kb in length, although another fragment 5.5 kb long was also identified. [9]

The PDHB gene encodes a precursor protein that has 359 amino acid residues and a final mature protein that has 329 amino acids, and is part of the pyruvate dehydrogenase multienzyme complex. [7] Two of the mature PDHB proteins come together with two PDHA proteins to form a heterotetrameric E1 subunit. Crystal Structures allowed for a model in which the enzyme undergoes a 2-A shuttle-like motion of its heterodimers to perform the catalysis. [10] Specifically, the catalytic residue has been identified on the PDHB subunit, the 89th residue, which is a glutamate. [11] In forming the entire PDH complex, the 289th beta residue, aspartic acid, interacts with the 276th residue of the E2 complex, a lysine. [12] The entire human complex is 9.5 MDa in size, and has been described as 60-meric, meaning there are over 60 components that are assembled to make the entire complex. These subunits are conserved across many species, as the function of this complex is essential for the generation of ATP for all eukaryotes. [13] Each component is responsible for the catalysis of one step in this pathway; this complex exists for the purpose of channeling the intermediates of each reaction to the next enzyme, thus greatly increasing the rate of reaction. [14]

Function

The pyruvate dehydrogenase complex is responsible for the oxidative decarboxylation of pyruvate, with the final product being Acetyl CoA. Overall the complex catalyzes five reactions, with the overall reaction being:

Pyruvate + CoA + NAD+ → acetyl-CoA + CO2

There are three different coenzymes required throughout the 5 steps that this complex carries out: thiamine pyrophosphate (TPP), lipoamide, and coenzyme A. This step is only one of the central metabolic pathway carried out by eukaryotes, in which glucose is oxidized to form carbon dioxide, water, and ATP. The E1 complex specifically uses the TPP cofactor to cleave the Calpha-C(=O) bond of pyruvate, and then transfer the acetyl group to the TPP coenzyme, thus resulting in an intermediate, hydroxylethyl-Tpp*E1, and producing CO2. The thiazolium ring on the TPP is ideal for adding to carbonyl groups and acting as an electron sink, or a group that can pull electrons from a reaction and stabilize an electron-deficient intermediate. [14] Additionally, PDHB interacts with Prolyl-hydroxylase PHD3 to regulate the cellular PDH activity. [15]

Clinical significance

Mutations in the PDHB gene have been known to cause one form of pyruvate dehydrogenase deficiency. Pyruvate dehydrogenase deficiency is characterized by the buildup of a chemical called lactic acid in the body and a variety of neurological problems. Signs and symptoms of this condition usually first appear shortly after birth, and they can vary widely among affected individuals. The most common feature is a potentially life-threatening buildup of lactic acid (lactic acidosis), which can cause nausea, vomiting, severe breathing problems, and an abnormal heartbeat. People with pyruvate dehydrogenase deficiency usually have neurological problems as well. Most have delayed development of mental abilities and motor skills such as sitting and walking. Other neurological problems can include intellectual disability, seizures, weak muscle tone (hypotonia), poor coordination, and difficulty walking. Some affected individuals have abnormal brain structures, such as underdevelopment of the tissue connecting the left and right halves of the brain (corpus callosum), wasting away (atrophy) of the exterior part of the brain known as the cerebral cortex, or patches of damaged tissue (lesions) on some parts of the brain. Because of the severe health effects, many individuals with pyruvate dehydrogenase deficiency do not survive past childhood, although some may live into adolescence or adulthood. [5] Most cases of pyruvate dehydrogenase complex (PDHc) deficiency are attributable to mutations in the PDHA1 gene which encodes the E(1)α subunit, with few cases of mutations in the genes for E3, E3BP, and E2 being described. However, there are a few cases in which mutations in the beta subunit gene have resulted in patients with Leigh syndrome. [16] Many pathological mutations have been described, including: R36C, which results in conformational change due to increased amino acid interactions; C306R, overall affecting interaction of the two beta subunits; I142M, affecting conformation around a potassium ion, thereby reducing PDHB stability; W165S, which also affects hydrophobic interaction between the beta subunits; and Y132C. [17] Other cases have been described in which there are no pathological mutations, but inborn errors of metabolism, specifically related to ubiquitination and proteasome machineries, resulted in a PDHB deficiency. This was demonstrated by PDH activity being restored in cells that were treated with MG132, which is known as proteasome inhibitor. [18] The clinical manifestations of this deficiency are similar to those of PDHA1 deficiency, with the exception being that ataxia is less frequent in these cases, and that consanguinity was found only in families with the PDHB deficiency. [17]

Interactive pathway map

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

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WP534.png go to articlego to articlego to articlego to articlego to articlego to articlego to articlego to articlego to articlego to articlego to articlego to articlego to articlego to articlego to articlego to articlego to articlego to articlego to articlego to articlego to articlego to articlego to articlego to articlego to articlego to articlego to articlego to articlego to articlego to articlego to articlego to articlego to articlego to articlego to articlego to articlego to articlego to articlego to articlego to articlego to articlego to articlego to articlego to articlego to articlego to articlego to articlego to articlego to articlego to articlego to articlego to articlego to articlego to articlego to articlego to articlego to articlego to articlego to articlego to articlego to articlego to articlego to articlego to articlego to articlego to articlego to articlego to articlego to articlego to articlego to WikiPathwaysgo to articlego to Entrezgo to article
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  1. The interactive pathway map can be edited at WikiPathways: "GlycolysisGluconeogenesis_WP534".

Related Research Articles

<span class="mw-page-title-main">Pyruvate dehydrogenase complex</span> Three-enzyme complex

Pyruvate dehydrogenase complex (PDC) is a complex of three enzymes that converts pyruvate into acetyl-CoA by a process called pyruvate decarboxylation. 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. Pyruvate decarboxylation is also known as the "pyruvate dehydrogenase reaction" because it also involves the oxidation of pyruvate.

<span class="mw-page-title-main">Pyruvate dehydrogenase lipoamide kinase isozyme 1</span> Protein-coding gene in the species Homo sapiens

Pyruvate dehydrogenase lipoamide kinase isozyme 1, mitochondrial is an enzyme that in humans is encoded by the PDK1 gene. It codes for an isozyme of pyruvate dehydrogenase kinase (PDK).

The branched-chain α-ketoacid dehydrogenase complex is a multi-subunit complex of enzymes that is found on the mitochondrial inner membrane. This enzyme complex catalyzes the oxidative decarboxylation of branched, short-chain alpha-ketoacids. BCKDC is a member of the mitochondrial α-ketoacid dehydrogenase complex family, which also includes pyruvate dehydrogenase and alpha-ketoglutarate dehydrogenase, key enzymes that function in the Krebs cycle.

Pyruvate dehydrogenase deficiency is a rare neurodegenerative disorder associated with abnormal mitochondrial metabolism. PDCD is a genetic disease resulting from mutations in one of the components of the pyruvate dehydrogenase complex (PDC). The PDC is a multi-enzyme complex that plays a vital role as a key regulatory step in the central pathways of energy metabolism in the mitochondria. The disorder shows heterogeneous characteristics in both clinical presentation and biochemical abnormality.

<span class="mw-page-title-main">Dihydrolipoyl transacetylase</span> Enzyme

Dihydrolipoyl transacetylase is an enzyme component of the multienzyme pyruvate dehydrogenase complex. The pyruvate dehydrogenase complex is responsible for the pyruvate decarboxylation step that links glycolysis to the citric acid cycle. This involves the transformation of pyruvate from glycolysis into acetyl-CoA which is then used in the citric acid cycle to carry out cellular respiration.

Oxidative decarboxylation is a decarboxylation reaction caused by oxidation. Most are accompanied by α- Ketoglutarate α- Decarboxylation caused by dehydrogenation of hydroxyl carboxylic acids such as carbonyl carboxylic acid, malic acid, isocitric acid, etc.

<span class="mw-page-title-main">Pyruvate dehydrogenase</span> Class of enzymes

Pyruvate dehydrogenase is an enzyme that catalyzes the reaction of pyruvate and a lipoamide to give the acetylated dihydrolipoamide and carbon dioxide. The conversion requires the coenzyme thiamine pyrophosphate.

<span class="mw-page-title-main">Dihydrolipoamide dehydrogenase</span> Protein-coding gene in the species Homo sapiens

Dihydrolipoamide dehydrogenase (DLD), also known as dihydrolipoyl dehydrogenase, mitochondrial, is an enzyme that in humans is encoded by the DLD gene. DLD is a flavoprotein enzyme that oxidizes dihydrolipoamide to lipoamide.

<span class="mw-page-title-main">E3 binding protein</span> Protein-coding gene in the species Homo sapiens

E3 binding protein also known as pyruvate dehydrogenase protein X component, mitochondrial is a protein that in humans is encoded by the PDHX gene. The E3 binding protein is a component of the pyruvate dehydrogenase complex found only in eukaryotes. Defects in this gene are a cause of pyruvate dehydrogenase deficiency which results in neurological dysfunction and lactic acidosis in infancy and early childhood. This protein is also a minor antigen for antimitochondrial antibodies. These autoantibodies are present in nearly 95% of patients with primary biliary cholangitis, an autoimmune disease of the liver. In primary biliary cholangitis, activated T lymphocytes attack and destroy epithelial cells in the bile duct where this protein is abnormally distributed and overexpressed. Primary biliary cholangitis eventually leads to liver failure.

<span class="mw-page-title-main">HADHA</span> Protein-coding gene in the species Homo sapiens

Trifunctional enzyme subunit alpha, mitochondrial also known as hydroxyacyl-CoA dehydrogenase/3-ketoacyl-CoA thiolase/enoyl-CoA hydratase, alpha subunit is a protein that in humans is encoded by the HADHA gene. Mutations in HADHA have been associated with trifunctional protein deficiency or long-chain 3-hydroxyacyl-coenzyme A dehydrogenase deficiency.

<span class="mw-page-title-main">Pyruvate dehydrogenase phosphatase</span> Protein-coding gene in the species Homo sapiens

Pyruvate dehydrogenase phosphatase catalytic subunit 1, also known as protein phosphatase 2C, is an enzyme that in humans is encoded by the PDP1 gene. PDPC 1 is an enzyme which serves to reverse the effects of pyruvate dehydrogenase kinase upon pyruvate dehydrogenase, activating pyruvate dehydrogenase.

<span class="mw-page-title-main">Pyruvate dehydrogenase (lipoamide) alpha 1</span> Protein-coding gene in the species Homo sapiens

Pyruvate dehydrogenase E1 component subunit alpha, somatic form, mitochondrial is an enzyme that in humans is encoded by the PDHA1 gene.The pyruvate dehydrogenase complex is a nuclear-encoded mitochondrial matrix multienzyme complex that provides the primary link between glycolysis and the tricarboxylic acid (TCA) cycle by catalyzing the irreversible conversion of pyruvate into acetyl-CoA. The PDH complex is composed of multiple copies of 3 enzymes: E1 (PDHA1); dihydrolipoyl transacetylase (DLAT) ; and dihydrolipoyl dehydrogenase (DLD). The E1 enzyme is a heterotetramer of 2 alpha and 2 beta subunits. The E1-alpha subunit contains the E1 active site and plays a key role in the function of the PDH complex.

<span class="mw-page-title-main">PDK4</span> Protein-coding gene in the species Homo sapiens

Pyruvate dehydrogenase lipoamide kinase isozyme 4, mitochondrial (PDK4) is an enzyme that in humans is encoded by the PDK4 gene. It codes for an isozyme of pyruvate dehydrogenase kinase.

<span class="mw-page-title-main">BCKDHA</span> Protein-coding gene in the species Homo sapiens

A 2-oxoisovalerate dehydrogenase subunit alpha, mitochondrial is an enzyme that in humans is encoded by the BCKDHA gene.

<span class="mw-page-title-main">DBT (gene)</span> Mammalian protein found in Homo sapiens

Lipoamide acyltransferase component of branched-chain alpha-keto acid dehydrogenase complex, mitochondrial is an enzyme that in humans is encoded by the DBT gene.

<span class="mw-page-title-main">PDK2</span> Protein-coding gene in the species Homo sapiens

Pyruvate dehydrogenase kinase isoform 2 (PDK2) also known as pyruvate dehydrogenase lipoamide kinase isozyme 2, mitochondrial is an enzyme that in humans is encoded by the PDK2 gene. PDK2 is an isozyme of pyruvate dehydrogenase kinase.

<span class="mw-page-title-main">BCKDHB</span> Protein-coding gene in the species Homo sapiens

2-Oxoisovalerate dehydrogenase subunit beta, mitochondrial is an enzyme that in humans is encoded by the BCKDHB gene.

<span class="mw-page-title-main">PDK3</span> Protein-coding gene in the species Homo sapiens

Pyruvate dehydrogenase lipoamide kinase isozyme 3, mitochondrial is an enzyme that in humans is encoded by the PDK3 gene. It codes for an isozyme of pyruvate dehydrogenase kinase.The pyruvate dehydrogenase (PDH) complex is a nuclear-encoded mitochondrial multienzyme complex that catalyzes the overall conversion of pyruvate to acetyl-CoA and CO2. It provides the primary link between glycolysis and the tricarboxylic acid (TCA) cycle, and thus is one of the major enzymes responsible for the regulation of glucose metabolism. The enzymatic activity of PDH is regulated by a phosphorylation/dephosphorylation cycle, and phosphorylation results in inactivation of PDH. The protein encoded by this gene is one of the four pyruvate dehydrogenase kinases that inhibits the PDH complex by phosphorylation of the E1 alpha subunit. This gene is predominantly expressed in the heart and skeletal muscles. Alternatively spliced transcript variants encoding different isoforms have been found for this gene.

<span class="mw-page-title-main">OGDH</span> Enzyme involved in Krebs cycle

Alpha-ketoglutarate dehydrogenase also known as 2-oxoglutarate dehydrogenase E1 component, mitochondrial is an enzyme that in humans is encoded by the OGDH gene.

<span class="mw-page-title-main">Pyruvate dehydrogenase (lipoamide) alpha 2</span> Protein-coding gene in the species Homo sapiens

Pyruvate dehydrogenase (lipoamide) alpha 2, also known as pyruvate dehydrogenase E1 component subunit alpha, testis-specific form, mitochondrial or PDHE1-A type II, is an enzyme that in humans is encoded by the PDHA2 gene.

References

  1. 1 2 3 GRCh38: Ensembl release 89: ENSG00000168291 Ensembl, May 2017
  2. 1 2 3 GRCm38: Ensembl release 89: ENSMUSG00000021748 Ensembl, May 2017
  3. "Human PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
  4. "Mouse PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
  5. 1 2 3 "Entrez Gene: pyruvate dehydrogenase (lipoamide) beta".
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Further reading

This article incorporates text from the United States National Library of Medicine, which is in the public domain.