Information on EC 2.3.1.135 - phosphatidylcholine-retinol O-acyltransferase and Organism(s) Homo sapiens

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


The taxonomic range for the selected organisms is: Homo sapiens

EC NUMBER
COMMENTARY hide
2.3.1.135
-
RECOMMENDED NAME
GeneOntology No.
phosphatidylcholine-retinol O-acyltransferase
REACTION
REACTION DIAGRAM
COMMENTARY hide
ORGANISM
UNIPROT
LITERATURE
phosphatidylcholine + retinol-[cellular-retinol-binding-protein] = 2-acylglycerophosphocholine + retinyl-ester-[cellular-retinol-binding-protein]
show the reaction diagram
REACTION TYPE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
Acyl group transfer
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-
-
-
PATHWAY
BRENDA Link
KEGG Link
MetaCyc Link
retinol biosynthesis
-
-
the visual cycle I (vertebrates)
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Retinol metabolism
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SYSTEMATIC NAME
IUBMB Comments
phosphatidylcholine:retinol---[cellular-retinol-binding-protein] O-acyltransferase
A key enzyme in retinoid metabolism, catalysing the transfer of an acyl group from the sn-1 position of phosphatidylcholine to retinol, forming retinyl esters which are then stored. Recognizes the substrate both in free form and when bound to cellular-retinol-binding-protein, but has higher affinity for the bound form. Can also esterify 11-cis-retinol.
CAS REGISTRY NUMBER
COMMENTARY hide
117444-03-8
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GENERAL INFORMATION
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
evolution
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based on its secondary structure LRAT belongs to a superfamily of enzymes generically referred as NIpC/P60. Within this superfamily, a multiple sequence alignment of LRAT and LRAT-like family members shows that they share three conserved amino acid residues; cysteine, histidine and a polar residue that is thought to complete a catalytic triad similar to the papain-like thiol peptidases
malfunction
metabolism
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the key step of vitamin A metabolism is the esterification of all-trans retinol, catalyzed by lecithin/retinol acyltransferase, LRAT. Vitamin A metabolism in benign and malignant melanocytic skin cells with regard to expression, functional activity of LRAT, RPE65, and cRBP2 and their regulation, overview
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
didecanoylphosphatidylcholine + all-trans-retinol
all-trans-retinyl decanoate + 2-decanoylglycerophosphocholine
show the reaction diagram
-
-
activity is about 10% of that with diheptanoylphosphatidylcholine
-
?
diheptanoylphosphatidylcholine + all-trans-retinol
all-trans-retinyl heptanoate + 2-heptanoylglycerophosphocholine
show the reaction diagram
-
-
-
-
?
dilauroylphosphatidylcholine + all-trans-retinol
all-trans-retinyl laurate + 2-lauroylglycerophosphocholine
show the reaction diagram
-
-
activity is about 4% of that with diheptanoylphosphatidylcholine
-
?
dimyristoylphosphatidylcholine + all-trans-retinol
all-trans-retinyl myristate + 2-myristoylglycerophosphocholine
show the reaction diagram
-
activity is about 3% of that with diheptanoylphosphatidylcholine
-
-
?
dioctanoylphosphatidylcholine + all-trans-retinol
all-trans-retinyl octanoate + 2-octanoylglycerophosphocholine
show the reaction diagram
-
activity is less than 15% of that with diheptanoylphosphatidylcholine
-
-
?
dioleoylphosphatidylcholine + all-trans-retinol
all-trans-retinyl oleate + 2-oleoylglycerophosphocholine
show the reaction diagram
-
-
-
-
?
dipalmitoylphosphatidylcholine + all-trans-retinol
all-trans-retinyl palmitate + 2-palmitoylglycerophosphocholine
show the reaction diagram
lecithin + retinol-[cellular retinol-binding protein]
2-acylglycerophosphocholine + retinyl ester-[cellular retinol-binding protein]
show the reaction diagram
-
-
-
-
?
phosphatidylcholine + 11-cis-retinol
2-acylglycerophosphocholine + 11-cis-retinyl acyl ester
show the reaction diagram
phosphatidylcholine + 11-cis-retinol
2-acylglycerophosphocholine + 11-cis-retinyl palmitate
show the reaction diagram
-
low activity
-
-
?
phosphatidylcholine + 11-cis-retinol-[cellular-retinol-binding-protein]
2-acylglycerophosphocholine + 11-cis-retinyl-ester-[cellular-retinol-binding-protein]
show the reaction diagram
phosphatidylcholine + all-trans-retinol
2-acylglycerophosphocholine + all-trans-retinyl acyl ester
show the reaction diagram
phosphatidylcholine + all-trans-retinol
2-acylglycerophosphocholine + all-trans-retinyl acylester
show the reaction diagram
phosphatidylcholine + all-trans-retinol
2-acylglycerophosphocholine + all-trans-retinyl palmitate
show the reaction diagram
-
-
-
-
?
phosphatidylcholine + all-trans-retinol
all-trans-retinyl acyl esters + 2-acylglycerophosphocholine
show the reaction diagram
phosphatidylcholine + all-trans-retinol-(bovine serum albumin)
all-trans-retinyl acyl ester-(bovine serum albumin) + 2-acylglycerophosphocholine
show the reaction diagram
-
-
?
phosphatidylcholine + all-trans-retinol-[cellular-retinol-binding-protein]
2-acylglycerophosphocholine + all-trans-retinyl-ester-[cellular-retinol-binding-protein]
show the reaction diagram
phosphatidylcholine + retinol-(cellular-retinol-binding-protein)
2-acylglycerophosphocholine + retinyl ester-(cellular-retinol-binding-protein)
show the reaction diagram
phosphatidylcholine + retinol-[cellular-retinol-binding-protein]
2-acylglycerophosphocholine + retinyl-ester-[cellular-retinol-binding-protein]
show the reaction diagram
additional information
?
-
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
lecithin + retinol-[cellular retinol-binding protein]
2-acylglycerophosphocholine + retinyl ester-[cellular retinol-binding protein]
show the reaction diagram
-
-
-
-
?
phosphatidylcholine + 11-cis-retinol
2-acylglycerophosphocholine + 11-cis-retinyl acyl ester
show the reaction diagram
-
essential for generation of the precursor for 11-cis-retinal, the visual chromophore in the eye
-
-
?
phosphatidylcholine + 11-cis-retinol-[cellular-retinol-binding-protein]
2-acylglycerophosphocholine + 11-cis-retinyl-ester-[cellular-retinol-binding-protein]
show the reaction diagram
-
trans-esterification reaction is reversible, however in the presence of the isomerase, all-trans-retinyl esters are converted to 11-cis-retinol which is enzymatically oxidized to 11-cis-retinal, the chromophore of vision. Both all-trans-retinol and 11-cis-retinol are substrates for LRAT esterification, although all-transretinol is the preferred substrate.
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r
phosphatidylcholine + all-trans-retinol
2-acylglycerophosphocholine + all-trans-retinyl acyl ester
show the reaction diagram
-
enzyme is involved in vitamin A storage and mobilization
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r
phosphatidylcholine + all-trans-retinol
all-trans-retinyl acyl esters + 2-acylglycerophosphocholine
show the reaction diagram
phosphatidylcholine + all-trans-retinol-[cellular-retinol-binding-protein]
2-acylglycerophosphocholine + all-trans-retinyl-ester-[cellular-retinol-binding-protein]
show the reaction diagram
phosphatidylcholine + retinol-[cellular-retinol-binding-protein]
2-acylglycerophosphocholine + retinyl-ester-[cellular-retinol-binding-protein]
show the reaction diagram
additional information
?
-
INHIBITORS
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
N-ethylmaleimide
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0.001 mM, complete inhibition of retinol-(cellular-retinol-binding-protein)type II esterification
phenylmethylsulfonyl fluoride
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2 mM, 90% inhibition of retinol-(cellular-retinol-binding-protein)type II esterification
retinyl bromoacetate
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78% reduction of enzyme activity
additional information
-
ACTIVATING COMPOUND
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
SDS
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SDS is necessary for tLRAT extraction from cell lysates. tLRAT enzymatic activity drastically diminishes at SDS concentrations below 0.05% and remains unchanged when SDS concentration is increased from 0.05 to 1%. SDS is very important for tLRAT stability
KM VALUE [mM]
SUBSTRATE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
0.0001 - 0.055
all-trans-retinol
0.00024
all-trans-retinol-[cellular-retinol-binding-protein]
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pH and temperature not specified in the publication
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0.0005
retinol-(cellular-retinol-binding-protein)
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reaction with phosphatidylcholine
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additional information
additional information
-
TURNOVER NUMBER [1/s]
SUBSTRATE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
40.4
all-trans-retinol
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pH not specified in the publication, 20°C
kcat/KM VALUE [1/mMs-1]
SUBSTRATE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
730
all-trans-retinol
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pH not specified in the publication, 20°C
SPECIFIC ACTIVITY [µmol/min/mg]
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
additional information
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activity of recombinant mutant enzymes and recombinant truncated wild-type, overview
pH OPTIMUM
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
6
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assay at
9
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about
pH RANGE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
10
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80% of maximum activity
additional information
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pH profile of recombinant mutant enzymes and recombinant truncated wild-type
TEMPERATURE OPTIMUM
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
20
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assay at
20 - 25
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22
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assay at room temperature
TEMPERATURE RANGE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
35
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15% of maximum activity
SOURCE TISSUE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
SOURCE
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in the glomeruli of normal, neoplastic kidney sections
Manually annotated by BRENDA team
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mRNA expression in adult stage
Manually annotated by BRENDA team
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breast carcinoma cells have lower LRAT activity
Manually annotated by BRENDA team
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neoplastic and adjacent, non-neoplastic glandular breast tissue specimens from human patients, expression analysis, reduced enzyme expression, LRAT protein progressively decreases with a reduction in the degree of tumor differentiation in invasive breast carcinomas, overview
Manually annotated by BRENDA team
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skin, these cells have lower LRAT activity
Manually annotated by BRENDA team
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epidermal
Manually annotated by BRENDA team
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diverse cell lines
Manually annotated by BRENDA team
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mRNA expression in adult stage
Manually annotated by BRENDA team
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epithelial cells
Manually annotated by BRENDA team
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-
Manually annotated by BRENDA team
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mRNA expression
Manually annotated by BRENDA team
additional information
LOCALIZATION
ORGANISM
UNIPROT
COMMENTARY hide
GeneOntology No.
LITERATURE
SOURCE
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before initiation of retinyl ester biosynthesis, LRAT distributes throughout the endoplasmic reticulum, and Crpb1 localizes with mitochondria associated membranes, surrounded by LRAT. Upon initiating retinyl ester biosynthesis in cells, Crpb1 remains with MAM, and both Crbp1 and MAM re-localize with LRAT. LRAT formed rings around the growing lipid droplets
Manually annotated by BRENDA team
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upon initiating retinyl ester biosynthesis in cells, Crpb1 remains with MAM, and both Crbp1 and MAM re-localize with LRAT. LRAT formed rings around the growing lipid droplets. LRAT-containing rings colocalize with the lipid-droplet surface proteins, desnutrin/adipose triglyceride lipase and perilipin 2. Colocalization with lipid droplets requires the 38 N-terminal amino acid residues of LRAT, and specifically K36 and R38. Formation of rings around the growing lipid droplets does not require functional microtubules
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Manually annotated by BRENDA team
additional information
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subcellular localization study, overview
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Manually annotated by BRENDA team
MOLECULAR WEIGHT
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
20000
-
1 * 25000, full-length wild-type enzyme, SDS-PAGE, 1 * 20000, recombinant truncated enzyme, SDS-PAGE; 2 * 25000, full-length wild-type enzyme, SDS-PAGE, 2 * 20000, recombinant truncated enzyme, SDS-PAGE
20900
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x * 20900
40000
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nonreducing PAGE, higher aggregation, up to pentamers, occurs in absence of denaturing agents
SUBUNITS
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
dimer
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2 * 25000, full-length wild-type enzyme, SDS-PAGE, 2 * 20000, recombinant truncated enzyme, SDS-PAGE
monomer
additional information
-
the enzyme exists as a mixture of monomer and dimer, determined by sedimentation equilibrium analysis and mass spectrometry, higher aggregation, up to pentamers, occurs in absence of denaturing agents
pH STABILITY
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
10.4
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inactivation of recombinant truncated wild-type enzyme, reversible by dialysis against a buffer with pH 8.4
658075
STORAGE STABILITY
ORGANISM
UNIPROT
LITERATURE
-70°C, 100 mM Tris-HCl, pH 8.3, 0.4% Triton X-100, stable for several days
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Purification/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
enzyme transfected in HEK-293T cells partially purificated by solubilization and centrifugation
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recombinant His-tagged LRAT by affinity chromatography
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recombinant His-tagged truncated wild-type and mutant enzymes from Escherichia coli strain BL21(DE3) by nickel affinity chromatography in presence of 1% SDS
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recombinant truncated enzyme from Escherichia coli in presence of 1% SDS, by nickel affinity chromatography to homogeneity
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recombinant truncated tLRAT and its S175R mutant
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SDS is necessary for tLRAT extraction from cell lysates. tLRAT enzymatic activity drastically diminishes at SDS concentrations below 0.05% and remains unchanged when SDS concentration is increased from 0.05 to 1%. SDS is very important for tLRAT stability. Detergents such as 0.2% Triton X-100, 0.7% CHAPSO,and 1.2 mM n-dodecyl-beta-D-maltoside and sodium are not effective
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Cloned/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
DNA sequence determination and analysis of the full length gene including the 3'- and 5'-ends, genetic organization analysis, at least 2 splicing variants, the second of which lacks a 103 nt polynucleotide in the 5'-UTR of the full length transcript
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expression in HEK-293 cells; expression in HEK-293T cells
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expression in HEK-293T cells
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expression of a truncated enzyme form lacking the transmembrane N- and C-termini in Escherichia coli as His-tagged protein, which is insoluble in absence of detergents
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expression of His-tagged truncated wild-type enzyme and His-tagged mutant enzymes in Escherichia coli strain BL21(DE3)
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gene lrat is localized on chromosome 4 at locus 4q31.2
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LRAT, quantitative real-time RT-PCR expression analysis in melanoma cell lines
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recombinant expression of His-tagged LRAT
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recombinant expression of the truncated tLRAT and its S175R mutant
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stable expression of GFP-tagged LRAT in CHO cells and of GFP-tagged LRAT in COS7 cells
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EXPRESSION
ORGANISM
UNIPROT
LITERATURE
expression of LRAT and RPE65 can be modulated by retinoids
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ENGINEERING
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
K104A
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site-directed mutagenesis, reduced activity compared to the truncated wild-type enzyme
K133A
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site-directed mutagenesis, increased activity compared to the truncated wild-type enzyme
K133A/K134A
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site-directed mutagenesis, slightly increased activity compared to the truncated wild-type enzyme
K134A
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site-directed mutagenesis, increased activity compared to the truncated wild-type enzyme
K147A
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site-directed mutagenesis, reduced activity compared to the truncated wild-type enzyme
K180A
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site-directed mutagenesis, nearly inactive mutant
K180R
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site-directed mutagenesis, reduced activity compared to the truncated wild-type enzyme
K186A
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site-directed mutagenesis, nearly inactive mutant
K186R
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site-directed mutagenesis, reduced activity compared to the truncated wild-type enzyme
K90A
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site-directed mutagenesis, highly reduced activity compared to the truncated wild-type enzyme
K95A
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site-directed mutagenesis, highly reduced activity compared to the truncated wild-type enzyme
Y118F
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site-directed mutagenesis, activity similar to the truncated wild-type enzyme
Y154F
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site-directed mutagenesis, inactive mutant
Y167F
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site-directed mutagenesis, activity similar to the truncated wild-type enzyme
Y64F
-
site-directed mutagenesis, highly increased activity compared to the truncated wild-type enzyme
additional information
APPLICATION
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
analysis
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ARPE-19 cell system is appropriate for studying the visual cycle enzymes
diagnostics
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enzyme might be a prognostic or therapeutic marker in renal cancer
medicine