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The enzyme 11-cis-retinyl-palmitate hydrolase (EC 3.1.1.63) catalyzes the reaction 11-cis-retinyl palmitate + H 2 O 11-cis-retinol + palmitate. This enzyme belongs to the family of hydrolases, specifically those acting on carboxylic ester bonds. The systematic name is 11-cis-retinyl-palmitate acylhydrolase.
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]
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 .
The basic structure of the hydrophobic retinoid molecule consists of a cyclic end group, a polyene side chain and a polar end group. The conjugated system formed by alternating C=C double bonds in the polyene side chain are responsible for the color of retinoids (typically yellow, orange, or red).
The primary dietary form is retinol, which may have a fatty acid molecule attached, creating a retinyl ester, when stored in the liver. Retinol – the transport and storage form of vitamin A – is interconvertible with retinal, catalyzed to retinal by retinol dehydrogenases and back to retinol by retinaldehyde reductases. [11]
The enzyme retinoid isomerohydrolase (EC 3.1.1.64, all-trans-retinyl-palmitate hydrolase) catalyzes the reaction 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.
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 ...
Retinol-binding proteins (RBP) are a family of proteins with diverse functions. They are carrier proteins that bind retinol.Assessment of retinol-binding protein is used to determine visceral protein mass in health-related nutritional studies.