2.3.1.135: phosphatidylcholine-retinol O-acyltransferase
This is an abbreviated version!
For detailed information about phosphatidylcholine-retinol O-acyltransferase, go to the full flat file.
Word Map on EC 2.3.1.135
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2.3.1.135
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retinoids
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retinal
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all-trans-retinyl
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opsin
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11-cis-retinol
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isomerohydrolase
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amaurosis
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leber
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s-opsins
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11-cis-retinoids
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medicine
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crbp-i
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diagnostics
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analysis
- 2.3.1.135
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retinoids
- retinal
-
all-trans-retinyl
- opsin
- 11-cis-retinol
-
isomerohydrolase
- amaurosis
-
leber
-
s-opsins
-
11-cis-retinoids
- medicine
-
crbp-i
- diagnostics
- analysis
Reaction
Synonyms
11-cis-acyl-CoA:retinol O-acyltransferase, acyltransferase, lecithin-retinol, EC 5.2.1.3, lecithin retinol acyl transferase, lecithin retinol acyltransferase, lecithin-retinol acyltransferase, lecithin/retinol acyltransferase, lecithin: retinol acyltransferase, lecithin:retinol acyl transferase, lecithin:retinol acyltransferase, LRAT, More, retinyl ester synthase, retinyl-ester synthase
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General Information
General Information on EC 2.3.1.135 - phosphatidylcholine-retinol O-acyltransferase
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evolution
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
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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
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
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a truncated form of LRAT as well as its S175R mutant lead to retinis pigmentosa, a severe form of retinal dystrophy
malfunction
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generation of an animal model in which the lrat gene is disrupted by homologous recombination gives Lrat-/- mice, which show slow degeneration of their retinas, essentially a shortening of rod outer segments and highly attenuated electroretinograms
malfunction
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homozygous mutation S175R occurs in two patients diagnosed with severe early-onset retinal degeneration
malfunction
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vitamin A uptake from recombinant holo-retinol-binding protein exhibited by wild-type mice is impaired in Lrat-deficient mice. Lrat-/- mice show elevated cellular vitamin A-binding protein 1, CRBP1, protein in the liver, lung, and adipose tissue as compared with wild type control animals
malfunction
Mus musculus C57/BL6J / 129 Sv
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vitamin A uptake from recombinant holo-retinol-binding protein exhibited by wild-type mice is impaired in Lrat-deficient mice. Lrat-/- mice show elevated cellular vitamin A-binding protein 1, CRBP1, protein in the liver, lung, and adipose tissue as compared with wild type control animals
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activities of LRAT and RPE65 may be important for removal of all-trans retinal which is the substrate for retinoic acid production in skin cells. Decreasing cellular amount of retinoic acid and its precursor molecules might result in a change of gene regulation
physiological function
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downregulation of LRAT expression in rat hepatic stellate cells is required for mobilization of retinyl ester in liver injury for tissue repair and wound healing, interleukin-1 is a potent suppressor of LRAT with a hierarchy role in the transcriptional regulation, interleukin-1 does not regulate the stability of LRAT protein. Interleukin-1 is a key mediator to down-regulate LRAT in liver injury
physiological function
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function of LRAT is to catalyze a trans-esterification reaction that occurs between the sn-1 position of lecithin molecules in the lipid bilayer of the smooth endoplasmic reticulum and all-trans-retinol in the formation of all-trans-retinyl esters. Functional role of LRAT in the visual cycle
physiological function
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function of LRAT is to catalyze a trans-esterification reaction that occurs between the sn-1 position of lecithin molecules in the lipid bilayer of the smooth endoplasmic reticulum and all-trans-retinol in the formation of all-trans-retinyl esters. Functional role of LRAT in the visual cycle
physiological function
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lecithin:retinol acyltransferase is critical for cellular uptake of vitamin A from serum retinol-binding protein, which depends on functional coupling of STRA6 with intracellular lecithin:retinol acyltransferase. Vitamin A uptake is regulated by all-trans-retinoic acid in nonocular tissues of mice. When in excess, vitamin A is rapidly taken up and converted to its inert ester form in peripheral tissues, such as lung, whereas in vitamin A deficiency, ocular retinoid uptake is favored
physiological function
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lecithin:retinol acyltransferase, LRAT, is a membrane-bound protein that plays an essential function in the visual cycle. It catalyzes the esterification of retinol into retinyl esters in the retinal pigment epithelium as well as in other tissues including testis, liver, and intestine
physiological function
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relationship between LRAT and Crbp1 during retinyl ester biosynthesis in which mitochondria associated membranes-associated Crpb1 and LRAT colocalize, and both surround the growing retinyl ester-containing lipid droplet. The N-terminus of LRAT, especially K36 and R38, is essential to colocalization with the lipid droplet
physiological function
cellular retinol-binding protein CRBP I effectively conveys retinol to the LRAT, thereby circumventing the low enzymatic activity of LRAT in polar bear livers
physiological function
quiescent LRAT knockout hepatic stellate cells retain the capacity to synthesize retinyl esters and to store neutral lipids in lipid droplets ex vivo. The median lipid droplet size in LRAT knockout hepatic stellate cells (1080 nm) is significantly smaller than in wild-type stellate cells (1618 nm). Upon prolonged (24h) incubation, the amounts of small (less than 700 nm) lipid droplets strongly increases both in wild type and in LRAT knockout hepatic stellate cells
physiological function
quiescent LRAT knockout hepatic stellate cells retain the capacity to synthesize retinyl esters and to store neutral lipids in lipid droplets ex vivo. The median lipid droplet size in LRAT knockout hepatic stellate cells (1080 nm) is significantly smaller than in wild-type stellate cells (1618 nm). Upon prolonged (24h) incubation, the amounts of small (less than 700 nm) lipid droplets strongly increases both in wild type and in LRAT knockout hepatic stellate cells
physiological function
retinoid isomerohydrolase RPE65 palmitoylation level is highly regulated by lecithin:retinol acyltransferase (LRAT) enzyme. In the presence of LRAT substrate all-trans retinol, there is a significant decrease in the level of palmitoylation of RPE65
physiological function
Mus musculus C57/BL6J / 129 Sv
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lecithin:retinol acyltransferase is critical for cellular uptake of vitamin A from serum retinol-binding protein, which depends on functional coupling of STRA6 with intracellular lecithin:retinol acyltransferase. Vitamin A uptake is regulated by all-trans-retinoic acid in nonocular tissues of mice. When in excess, vitamin A is rapidly taken up and converted to its inert ester form in peripheral tissues, such as lung, whereas in vitamin A deficiency, ocular retinoid uptake is favored
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malignant melanoma cells are able to esterify all-trans retinol and subsequently isomerize all-trans retinyl esters into 11-cis retinol, whereas their benign counterpart melanocytes are not able to catalyze these reactions
additional information
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the catalytic triad includes histidine 60, tyrosine 154 and cysteine 161 in the LRAT structure