Information on EC 1.14.14.23 - cholesterol 7alpha-monooxygenase

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The expected taxonomic range for this enzyme is: Eukaryota, Bacteria

EC NUMBER
COMMENTARY hide
1.14.14.23
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RECOMMENDED NAME
GeneOntology No.
cholesterol 7alpha-monooxygenase
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REACTION
REACTION DIAGRAM
COMMENTARY hide
ORGANISM
UNIPROT
LITERATURE
cholesterol + [reduced NADPH-hemoprotein reductase] + O2 = 7alpha-hydroxycholesterol + [oxidized NADPH-hemoprotein reductase] + H2O
show the reaction diagram
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REACTION TYPE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
oxidation
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redox reaction
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reduction
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PATHWAY
BRENDA Link
KEGG Link
MetaCyc Link
bile acid biosynthesis, neutral pathway
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Metabolic pathways
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Primary bile acid biosynthesis
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Steroid hormone biosynthesis
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bile acid biosynthesis, neutral pathway
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SYSTEMATIC NAME
IUBMB Comments
cholesterol,NADPH-hemoprotein reductase:oxygen oxidoreductase (7alpha-hydroxylating)
A P-450 heme-thiolate liver protein that catalyses the first step in the biosynthesis of bile acids. The direct electron donor to the enzyme is EC 1.6.2.4, NADPH---hemoprotein reductase.
CAS REGISTRY NUMBER
COMMENTARY hide
9037-53-0
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ORGANISM
COMMENTARY hide
LITERATURE
UNIPROT
SEQUENCE DB
SOURCE
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Manually annotated by BRENDA team
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SwissProt
Manually annotated by BRENDA team
gene CYP125A4
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Manually annotated by BRENDA team
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Manually annotated by BRENDA team
GENERAL INFORMATION
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
evolution
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the enzyme belongs to the cytochrome P450 family
malfunction
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heat shock factor-1 ablation not only eliminates heat shock response, but it also transcriptionally upregulates CYP7A1 and MDR1/P-gp axis in atherogenic western diet-diet fed HSF-1 and low density lipoproteins receptor double knock out mice to reduce atherosclerosis
metabolism
physiological function
additional information
SUBSTRATE
PRODUCT                       
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate) hide
LITERATURE
(Substrate)
COMMENTARY
(Product) hide
LITERATURE
(Product)
Reversibility
r=reversible
ir=irreversible
?=not specified
25-hydroxycholesterol + [reduced NADPH-hemoprotein reductase] + O2
?
show the reaction diagram
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?
27-hydroxycholesterol + [reduced NADPH-hemoprotein reductase] + O2
?
show the reaction diagram
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?
5alpha-cholestan-3beta-ol + NADPH + O2
5alpha-cholestan-3beta,7alpha-diol + NADP+ + H2O
show the reaction diagram
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?
7-dehydrocholesterol + NADPH + H+
7-oxocholesterol + NADP+ + H2O
show the reaction diagram
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minor product: 7alpha,8alpha-epoxide, reaction with 7-[2H1]dehydrocholesterol yields complete migration of deuterium in the product 7-oxocholesterol. Minor product: 7alpha8alpha-epoxide
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?
cholest-4-en-3-one + [reduced NADPH-hemoprotein reductase] + O2
?
show the reaction diagram
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?
cholesterol + [reduced NADPH-hemoprotein reductase] + O2
7alpha-hydroxycholesterol + [oxidized NADPH-hemoprotein reductase] + H2O
show the reaction diagram
cholesterol + [reduced NADPH-hemoprotein reductase] + O2
7alpha-hydroxycholesterol + [oxidized NADPH—hemoprotein reductase] + H2O
show the reaction diagram
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stereospecific hydroxylation of cholesterol
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?
lathosterol + NADPH + H+
7-oxocholestanol + cholestanol-7alpha,8alpha-epoxide + NADP+ + H2O
show the reaction diagram
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i.e. DELTA-dihydro-7-dehydrocholesterol
about 1:2 ratio of 7-oxo and epoxide products, the epoxide does not rearrange to the ketone
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?
additional information
?
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NATURAL SUBSTRATES
NATURAL PRODUCTS
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate) hide
LITERATURE
(Substrate)
COMMENTARY
(Product) hide
LITERATURE
(Product)
REVERSIBILITY
r=reversible
ir=irreversible
?=not specified
7-dehydrocholesterol + NADPH + H+
7-oxocholesterol + NADP+ + H2O
show the reaction diagram
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minor product: 7alpha,8alpha-epoxide
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?
cholesterol + [reduced NADPH-hemoprotein reductase] + O2
7alpha-hydroxycholesterol + [oxidized NADPH-hemoprotein reductase] + H2O
show the reaction diagram
lathosterol + NADPH + H+
7-oxocholestanol + cholestanol-7alpha,8alpha-epoxide + NADP+ + H2O
show the reaction diagram
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i.e. DELTA-dihydro-7-dehydrocholesterol
about 1:2 ratio of 7-oxo and epoxide products, the epoxide does not rearrange to the ketone
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?
additional information
?
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COFACTOR
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
cytochrome b5
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essential component of the cholesterol 7alpha-hydroxylase system
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NADPH
INHIBITORS
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
bile acid
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feedback inhibition preventing the accumulation of cytotoxic hydrophobic bile acids
taurochenodeoxycholate
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70% inhibition at 0.1 mM
additional information
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ACTIVATING COMPOUND
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
2,4,6-trihydroxyacetophenone
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CYP7A1 induction, 166%, and activation, 160%, by 2,4,6-trihydroxyacetophenone, which also antagonizes the inhibition of CYP7A1 expression by chenodeoxycholic acid
dithiothreitol
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Thiol-containing substances
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e.g. mercaptoethanol, dithiothreitol or cysteamine enhance activity
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Triton X-100
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stimulates
additional information
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KM VALUE [mM]
SUBSTRATE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
0.0011
7-dehydrocholesterol
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pH 7.4, 30°C
0.015 - 0.052
cholesterol
0.0018 - 0.0021
lathosterol
additional information
additional information
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TURNOVER NUMBER [1/s]
SUBSTRATE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
0.015
25-hydroxycholesterol
Homo sapiens
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pH 7.2, 37°C, wild-type enzyme
0.0685 - 0.117
27-Hydroxycholesterol
0.04
7-dehydrocholesterol
Homo sapiens
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pH 7.4, 30°C
0.003 - 0.117
cholest-4-en-3-one
0.008 - 0.833
cholesterol
0.06 - 0.12
lathosterol
kcat/KM VALUE [1/mMs-1]
SUBSTRATE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
30
7-dehydrocholesterol
Homo sapiens
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pH 7.4, 30°C
5120
30 - 50
lathosterol
9203
SPECIFIC ACTIVITY [µmol/min/mg]
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
0.0000034
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wild-type Hep-G2 cell microsomes
0.000022
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day 1 after hepatectomy
0.000048
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day 1 after sham operation
0.000058
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day 3 after sham operation
0.000065
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day 3 after hepatectomy
0.000069
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day 7 after hepatectomy
0.000075
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day 7 after sham operation
0.000092
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recombinant enzyme in transformed Hep-G2 cells
0.00015
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0.0006
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enzyme activity depends on circadian rhythm, minimum activity at 2 p.m.
0.00077
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after incubation with 1 unit alkaline phosphatase for 30 min
0.00092
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after incubation with 1 unit alkaline phosphatase for 30 min
0.001
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enzyme activity depends on circadian rhythm, maximum activity at 10 p.m.
0.00196
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0.00294
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after incubation with 5 units cAMP-dependent protein kinase for 30 min
0.00315
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after incubation with 5 units cAMP-dependent protein kinase for 30 min
additional information
pH OPTIMUM
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
7.2
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assay at
7.5
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assay at
TEMPERATURE OPTIMUM
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
SOURCE TISSUE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
SOURCE
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Mycobacterium smegmatis can grow on cholesterol as the sole carbon source
Manually annotated by BRENDA team
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HepG2 cell transformed with a cyp7alpha-reporter gene (promoter fragment fused to firefly luciferase)
Manually annotated by BRENDA team
additional information
MOLECULAR WEIGHT
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
50000
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x * 50000, approximately, SDS-PAGE
52000
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x * 52000, SDS-PAGE
53000
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x * 53000, SDS-PAGE
additional information
SUBUNITS
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
POSTTRANSLATIONAL MODIFICATION
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
phosphoprotein
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the enzyme is phosphorylated at multiple amino acids, overview
side-chain modification
additional information
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enzyme has a partial requirement for phospholipid
Crystallization/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
wild-type CYP7A1 in the ligand-free state, structure-based mutation T104L in the B' helix, corresponding to the nonpolar residue of CYP7B1, is used to obtain crystals of complexes with cholest-4-en-3 -one and with cholesterol oxidation product 7-ketocholesterol, hanging drop vapor diffusion method, mixing 0f 0.001 ml of protein solution with 0.001 ml of reservoir solution containing 0.1 M sodium chloride, 0.1 M trisodium citrate, pH 5.5, and 20% PEG 400, 18°C, to obtain a complex with cholest-4-en-3-one, a T104L mutant is used, and the crystals are grown in conditions containing 0.1 M MES, pH 6.0, and 18% PEG 550 monomethylether and soaked with 20% glycerol. For the T104L mutant-7KCh complex, crystals are grown in 0.1 M sodium chloride, 0.1 M tri-sodium citrate, pH 5.6, and 20% PEG 400, room temperature, X-ray diffraction structure determination and analysis at 1.90-2.75 A resolution
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GENERAL STABILITY
ORGANISM
UNIPROT
LITERATURE
rapid inactivation upon incubating microsomes with NADPH, half-life: 1 h, addition of dithiothreitol partially protects against inactivation
Purification/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
2 isoenzymes: I and II
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native and recombinant enzyme partially by microsome preparation
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partially from Hep-G2 cells by microsome preparation
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purification of cytochrome P-450
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purification of P-450 7alpha
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Cloned/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
Cyp7a1 expression pattern in wild-type and Cyp8b1 null mice livers, overview
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Cyp7a1-tg mice overexpressing rat Cyp7a1 complementary DNA under an ApoE3 hepatic control region
expressed in Mus musculus liver
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expression in Escherichia coli
expression of His6-tagged enzyme in Escherichia coli strain BL21(DE3), stable expression of CYP7A cDNA using the cytomegalovirus promoter and the bovine growth hormone polyadenylation signal in Hep-G2 cells
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gene CYP7A1, DNA sequence determination and analysis, phylogenetic tree, expression analysis and regulation, overview
gene Cyp7a1, enzyme expression analysis
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gene CYP7A1, genetic structure, the gene contains six exons and five introns and is located on chromosome 8 at 8q11-q12, CYP7A1 mRNA levels are regulated through the farnesoid X receptor and the liver X receptor by many stimuli including cholesterol, bile acids, cytokines, steroid hormones, and thyroid hormone
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gene CYP7A1, genotyping, overview. Expression of promoter constructs in HepG2 cells
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gene CYP7A1, transient expression in Hep-G2 cells
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gene CYP7AI, genotyping, overexpression of genetic variants in Hep-G2 cells
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mutant Cyp7A1 promoter fragment cloned luciferase construct is generated using wild-type CYP7A1 promoter cloned luciferase, the gene contains a HSF-1 binding site in the CYP7A1 promoter region, oligonucleotides corresponding to -922 to -901 bases
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native and mutated genes expressed in COS-1 cells
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recombinant enzyme expressed in transgenic mice
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EXPRESSION
ORGANISM
UNIPROT
LITERATURE
activation of an AMP-activated protein kinase decreases CYP7A1 mRNA, hepatocyte nuclear factor 4alpha protein, and binding to CYP7A1 chromatin
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apobec-1 knock-out mice show a decrease in cholesterol 7alpha-hydroxylase mRNA
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atorvastatin induces enzyme Cyp7a1 by suppressing FXR signaling in both liver and intestine. Atorvastatin suppresses the expression of bile acid nuclear receptor farnesoid X receptor (FXR) target genes, namely small heterodimer partner (liver) and fibroblast growth factor 15 (ileum). Atorvastatin increases the mRNAs of the organic cation uptake transporter 1 and cholesterol efflux transporters Abcg5 and Abcg8 in the liver
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atorvastatin induces enzyme Cyp7a1 by suppressing FXR signaling in both liver and intestine. Atorvastatin suppresses the expression of bile acid nuclear receptor farnesoid X receptor (FXR) target genes, namely small heterodimer partner (liver) and fibroblast growth factor 15 (ileum). Atorvastatin increases the mRNAs of the organic cation uptake transporter 1 and cholesterol efflux transporters Abcg5 and Abcg8 in the liver; in farnesoid X receptor-deficient and wild-type mice with hypercholesterolemia, injection of 1alpha,25-dihydroxyvitamin D3 consistently reduces levels of plasma and liver cholesterol and farnesoid X receptor small heterodimer partner, Shp, mRNA, and increases hepatic Cyp7a1 mRNA and protein. The transcription factors, liver receptor homolog-1 (NR5A2) and hepatocyte nuclear factor 4a (NR2A1), are essential for CYP7A1 expression
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bile acid-activated farnesoid X receptor, FXR, inhibits CYP7A1 transcription via activation of FGF15 receptor 4 signaling in hepatocytes, or via FGF19, that strongly inhibits CYP7A1 mRNA expression, overview. miR-122a and miR-422a may destabilize CYP7A1 mRNA to inhibit CYP7A1 expression, putative recognition sequences for miR-122a and miR-422a are localized in the 3'-UTR of human CYP7A1 mRNA
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Chlamydia pneumoniae and human cytomegalovirus infections significantly decrease isoform CYP7A1 promoter activity in a dose-dependent manner, with maximal inhibitions of 33% and 32%, respectively
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Cyp7a1 is a direct thyroid hormone target gene that responds to physiologic thyroid hormone levels through a set of distinct response elements in its promoter
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CYP7A1 mRNAs have very short half-lives, and bile acids destabilize CYP7A1 mRNA via the 3'-untranslated region
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CYP7A1 protein expression in chronic hypothyroid rats is significantly decreased
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expression is strongly repressed after 70% partial hepatectomy (during liver regeneration)
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fibroblast growth factor 19 inhibits cholesterol 7alpha-hydroxylase mRNA expression
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Forkhead box transcription factor O1 inhibits cholesterol 7alpha-hydroxylase mRNA expression
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Forkhead box transcription factor O1 inhibits cholesterol 7alpha-hydroxylase mRNA expression in livers of high fat diet-fed mice
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heat shock factor-1 knockout enhances cholesterol 7alpha hydroxylase (CYP7A1) and multidrug transporter (MDR1) gene expressions to attenuate atherosclerosis
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high glucose stimulates bile acid synthesis and induces mRNA expression of cholesterol 7alpha-hydroxylase, the key regulatory gene in bile acid synthesis. Glucose increased ATP levels to inhibit AMPK and induce HNF4alpha to stimulate CYP7A1 gene transcription. Knockdown of ATP-citrate lyase, which converts citrate to acetyl-CoA, decreases histone acetylation, and attenuates glucose induction of CYP7A1 mRNA expression
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in farnesoid X receptor-deficient and wild-type mice with hypercholesterolemia, injection of 1alpha,25-dihydroxyvitamin D3 consistently reduces levels of plasma and liver cholesterol and farnesoid X receptor small heterodimer partner Shp mRNA, and increases hepatic Cyp7a1 mRNA and protein. The transcription factors, liver receptor homolog-1 (NR5A2) and hepatocyte nuclear factor 4a (NR2A1), are essential for CYP7A1 expression
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in farnesoid X receptor-deficient and wild-type mice with hypercholesterolemia, injection of 1alpha,25-dihydroxyvitamin D3 consistently reduces levels of plasma and liver cholesterol and farnesoid X receptor small heterodimer partner, Shp, mRNA, and increases hepatic Cyp7a1 mRNA and protein. The transcription factors, liver receptor homolog-1 (NR5A2) and hepatocyte nuclear factor 4a (NR2A1), are essential for CYP7A1 expression
increase in cholesterol 7alpha-hydroxylase mRNA expression at 16 h (10 h of light) demonstrates a shift in the diurnal rhythm at day 10 postpartum
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lithocholic acid-acetate and 1alpha,25-dihydroxy-vitamin D3 inhibit cholesterol 7alpha-hydroxylase mRNA expression
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postpartum: increase in mRNA and protein levels of cholesterol 7alpha-hydroxylase; significant increase in Cyp7a1 levels in neonatal hamsters is due to mechanisms independent of the FXR and SHP pathway and cortisol. Precocious expression of Cyp7a1 can not be induced in neonatal hamsters with dexamethasone
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rodent Cyp7a1 expression increases in response to cholesterol-enriched diets, resulting in increased bile acid synthesis
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several negative feedback loops within the liver and small intestine down-regulate Cyp7a1 transcription to prevent accumulation of bile acids to toxic levels. The the JNK/c-Jun pathway is involved in downregulation of Cyp7a1, overview
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several nutritive peptides inhibit luciferase expression (cyp7alpha-reporter gene (promoter fragment fused to firefly luciferase))
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the amount of methionine and cystine in a diet affects cholesterol 7 alpha-hydroxylase activity
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upregulation of CYP7A1 mRNA in hypercholesterolemic rats treated with extracts from steamed and dried roots of Panax ginseng C.A. Meyer, and upregulation of CYP7A1 mRNA and protein levels by the addition of ginsenosides Ro, Rg3, Re, Rg1, and Rg2 to rat primary hepatocytes
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ENGINEERING
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
A204C
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nucleotide exchange, a naturally occuring promoter polymorphism in the CYP7A1 gene, the genetic variant shows less total cholesterol level decrease in response to dietary changes in different types of dietary intervention studies compared to C204 homozygotes, overview
A278C
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nucleotide exchange, a naturally occuring promoter polymorphism in the CYP7A1 gene
C16A
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strongly decreased activity
C175A
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decreased activity
C17A
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increased activity
C444A
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no activity
C44A
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decreased activity
C476A
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no activity
C554T
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nucleotide exchange, a naturally occuring promoter polymorphism in the CYP7A1 gene
C69A
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no effect on activity
C90A
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decreased activity
T104L
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the mutant is similar to the wild-type in ligand binding and catalytic properties and readily crystallizes with substrates. The structure of the T104L mutant in complex with cholest-4-en-3-one explicitly identifies key residues involved in 7alpha-hydroxylation
additional information
APPLICATION
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
analysis
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development of a straightforward dual-reporter bioluminescent assay to simultaneously monitor isoform CYP7A1 transcriptional regulation and cell viability in Chlamydia pneumoniae and human cytomegalovirus infected human hepatoblastoma Hep-G2 cells
medicine