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Retinyl palmitate, or vitamin A palmitate, is the ester of retinol and palmitic acid, with formula C 36 H 60 O 2. It is the most abundant form of vitamin A storage in animals. [2] An alternate spelling, retinol palmitate, which violates the -yl organic chemical naming convention for esters, is also frequently seen. [citation needed]
The enzyme 11-cis-retinyl-palmitate hydrolase (EC 3.1.1.63) catalyzes the reaction 11- cis -retinyl palmitate + H 2 O ⇌ {\displaystyle \rightleftharpoons } 11- cis -retinol + palmitate This enzyme belongs to the family of hydrolases , specifically those acting on carboxylic ester bonds.
an all-trans-retinyl ester + H 2 O = 11-cis-retinol + a fatty acid. This enzyme belongs to the family of hydrolases, specifically those acting on carboxylic ester bonds. The systematic name is all-trans-retinyl ester acylhydrolase, 11-cis retinol-forming. This enzyme participates in retinol metabolism.
Vitamin A occurs as two principal forms in foods: A) retinoids, found in animal-sourced foods, either as retinol or bound to a fatty acid to become a retinyl ester, and B) the carotenoids α-carotene (alpha-carotene), β-carotene, γ-carotene (gamma-carotene), and the xanthophyll beta-cryptoxanthin (all of which contain β-ionone rings) that ...
Retinal pigment epithelium-specific 65 kDa protein (also known as RPE65) is a retinoid isomerohydrolase enzyme of the vertebrate visual cycle. [5] [6] RPE65 is expressed in the retinal pigment epithelium (RPE, a layer of epithelial cells that nourish the photoreceptor cells) and is responsible for the conversion of all-trans-retinyl esters to 11-cis-retinol during phototransduction.
In enzymology, a retinyl-palmitate esterase (EC 3.1.1.21) is an enzyme that catalyzes the chemical reaction. retinyl palmitate + H 2 O ⇌ {\displaystyle \rightleftharpoons } retinol + palmitate Thus, the two substrates of this enzyme are retinyl palmitate and H 2 O , whereas its two products are retinol and palmitate .
Retinol, also called vitamin A 1, is a fat-soluble vitamin in the vitamin A family that is found in food and used as a dietary supplement. [3] Retinol or other forms of vitamin A are needed for vision, cellular development, maintenance of skin and mucous membranes, immune function and reproductive development. [3]
Retinyl esters can be distinguished from retinol in serum and other tissues and quantified with the use of methods such as high-performance liquid chromatography. [21] Elevated amounts of retinyl ester (i.e., >10% of total circulating vitamin A) in the fasting state have been used as markers for chronic hypervitaminosis A in humans and monkeys ...