Squalene monooxygenase

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Squalene epoxidase
Squalene epoxide biosynthesis.png
Chemical reaction catalyzed by squalene epoxidase.
Identifiers
EC no. 1.14.13.132
CAS no. 9029-62-3
Databases
IntEnz IntEnz view
BRENDA BRENDA entry
ExPASy NiceZyme view
KEGG KEGG entry
MetaCyc metabolic pathway
PRIAM profile
PDB structures RCSB PDB PDBe PDBsum
Gene Ontology AmiGO / QuickGO
Search
PMC articles
PubMed articles
NCBI proteins
SQLE
Identifiers
Aliases SQLE , entrez:6713, squalene epoxidase
External IDs OMIM: 602019 MGI: 109296 HomoloGene: 2355 GeneCards: SQLE
Orthologs
SpeciesHumanMouse
Entrez
Ensembl
UniProt
RefSeq (mRNA)

NM_003129

NM_009270

RefSeq (protein)

NP_003120

NP_033296

Location (UCSC) Chr 8: 125 – 125.02 Mb Chr 15: 59.19 – 59.2 Mb
PubMed search [3] [4]
Wikidata
View/Edit Human View/Edit Mouse

Squalene monooxygenase (also called squalene epoxidase) is a eukaryotic enzyme that uses NADPH and diatomic oxygen to oxidize squalene to 2,3-oxidosqualene (squalene epoxide). Squalene epoxidase catalyzes the first oxygenation step in sterol biosynthesis and is thought to be one of the rate-limiting enzymes in this pathway. [5] In humans, squalene epoxidase is encoded by the SQLE gene. [6] Several eukaryote genomes lack a squalene monooxygenase encoding gene, but instead encode an alternative squalene epoxidase that performs the same task. [7]

Contents

Mechanism

The canonical squalene monooxygenase is a flavoprotein monooxygenase. Flavoprotein monooxygenase form flavin hydroperoxides at the enzyme active site, which then transfer the terminal oxygen atom of the hydroperoxide to the substrate. Squalene monooxygenase differs from other flavin monooxygenases in that the oxygen is inserted into the substrate as an epoxide rather than as a hydroxyl group. This enzyme contains a loosely bound FAD flavin and obtains electrons from NADPH-cytochrome P450 reductase, rather than binding NADPH directly. The alternative squalene epoxidase belongs to the fatty acid hydroxylase superfamily and obtains electrons from cytochrome b5. [7]

Inhibitors

Inhibitors of squalene epoxidase have found application mainly as antifungal drugs: [8]

Since squalene epoxidase is on the biosynthetic pathway leading to cholesterol, inhibitors of this enzyme may also find application in treatment of hypercholesterolemia. [10]

Localization

In baker's yeast ( Saccharomyces cerevisiae ), squalene epoxidase is localized to both the endoplasmic reticulum and lipid droplets. Only the ER localized protein is active.

Additional products

Squalene epoxidase also catalyzes the formation of diepoxysqualene (DOS). DOS is converted to 24(S),25-epoxylanosterol by lanosterol synthase.

See also

Related Research Articles

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<span class="mw-page-title-main">Steroid 11β-hydroxylase</span> Protein found in mammals

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<span class="mw-page-title-main">Farnesyl-diphosphate farnesyltransferase</span> Class of enzymes

Squalene synthase (SQS) or farnesyl-diphosphate:farnesyl-diphosphate farnesyl transferase is an enzyme localized to the membrane of the endoplasmic reticulum. SQS participates in the isoprenoid biosynthetic pathway, catalyzing a two-step reaction in which two identical molecules of farnesyl pyrophosphate (FPP) are converted into squalene, with the consumption of NADPH. Catalysis by SQS is the first committed step in sterol synthesis, since the squalene produced is converted exclusively into various sterols, such as cholesterol, via a complex, multi-step pathway. SQS belongs to squalene/phytoene synthase family of proteins.

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NAD<sup>+</sup> kinase Enzyme

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<span class="mw-page-title-main">Flavin containing monooxygenase 1</span> Protein-coding gene in the species Homo sapiens

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<span class="mw-page-title-main">FMO5</span> Protein-coding gene in the species Homo sapiens

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<span class="mw-page-title-main">FMO2</span> Protein-coding gene in the species Homo sapiens

Dimethylaniline monooxygenase [N-oxide-forming] 2 is an enzyme that in humans is encoded by the FMO2 gene.

<span class="mw-page-title-main">FMO4</span> Protein-coding gene in the species Homo sapiens

Dimethylaniline monooxygenase [N-oxide-forming] 4 is an enzyme that in humans is encoded by the FMO4 gene.

<span class="mw-page-title-main">CYP4F12</span> Protein-coding gene in the species Homo sapiens

Cytochrome P450 4F12 is a protein that in humans is encoded by the CYP4F12 gene.

<span class="mw-page-title-main">ASRGL1</span> Protein-coding gene in the species Homo sapiens

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

Kynurenine 3-monooxygenase is an enzyme that in humans is encoded by the KMO gene.

<span class="mw-page-title-main">CYP4F22</span> Protein-coding gene in the species Homo sapiens

CYP4F22 is a protein that in humans is encoded by the CYP4F22 gene.

<span class="mw-page-title-main">ACAT2</span> Protein-coding gene in the species Homo sapiens

Acetyl-CoA acetyltransferase, cytosolic, also known as cytosolic acetoacetyl-CoA thiolase, is an enzyme that in humans is encoded by the ACAT2 gene

<span class="mw-page-title-main">Flavin-containing monooxygenase</span> Class of enzymes

The flavin-containing monooxygenase (FMO) protein family specializes in the oxidation of xeno-substrates in order to facilitate the excretion of these compounds from living organisms. These enzymes can oxidize a wide array of heteroatoms, particularly soft nucleophiles, such as amines, sulfides, and phosphites. This reaction requires an oxygen, an NADPH cofactor, and an FAD prosthetic group. FMOs share several structural features, such as a NADPH binding domain, FAD binding domain, and a conserved arginine residue present in the active site. Recently, FMO enzymes have received a great deal of attention from the pharmaceutical industry both as a drug target for various diseases and as a means to metabolize pro-drug compounds into active pharmaceuticals. These monooxygenases are often misclassified because they share activity profiles similar to those of cytochrome P450 (CYP450), which is the major contributor to oxidative xenobiotic metabolism. However, a key difference between the two enzymes lies in how they proceed to oxidize their respective substrates; CYP enzymes make use of an oxygenated heme prosthetic group, while the FMO family utilizes FAD to oxidize its substrates.

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

Biliverdin reductase B is a protein that in humans is encoded by the BLVRB gene.

References

  1. 1 2 3 GRCh38: Ensembl release 89: ENSG00000104549 - Ensembl, May 2017
  2. 1 2 3 GRCm38: Ensembl release 89: ENSMUSG00000022351 - 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. "Entrez Gene: SQLE squalene epoxidase".
  6. Nagai M, Sakakibara J, Wakui K, Fukushima Y, Igarashi S, Tsuji S, Arakawa M, Ono T (Aug 1997). "Localization of the squalene epoxidase gene (SQLE) to human chromosome region 8q24.1". Genomics. 44 (1): 141–3. doi:10.1006/geno.1997.4825. PMID   9286711.
  7. 1 2 Pollier J, Vancaester E, Kuzhiumparambil U, Vickers CE, Vandepoele K, Goossens A, Fabris M (2019). "A widespread alternative squalene epoxidase participates in eukaryote steroid biosynthesis". Nature Microbiology. 4 (2): 226–233. doi:10.1038/s41564-018-0305-5. hdl: 1854/LU-8587985 . PMID   30478288. S2CID   53726187.
  8. Favre B, Ryder NS (Feb 1996). "Characterization of squalene epoxidase activity from the dermatophyte Trichophyton rubrum and its inhibition by terbinafine and other antimycotic agents". Antimicrobial Agents and Chemotherapy. 40 (2): 443–7. doi:10.1128/AAC.40.2.443. PMC   163131 . PMID   8834895.
  9. Ryder NS (Feb 1992). "Terbinafine: mode of action and properties of the squalene epoxidase inhibition". The British Journal of Dermatology. 126 Suppl 39: 2–7. doi:10.1111/j.1365-2133.1992.tb00001.x. PMID   1543672. S2CID   19780957.
  10. Chugh A, Ray A, Gupta JB (Jan 2003). "Squalene epoxidase as hypocholesterolemic drug target revisited". Progress in Lipid Research. 42 (1): 37–50. doi:10.1016/S0163-7827(02)00029-2. PMID   12467639.

Further reading

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