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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.
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]
Vitamin A is a fat-soluble vitamin that is an essential nutrient.The term "vitamin A" encompasses a group of chemically related organic compounds that includes retinol, retinyl esters, and several provitamin (precursor) carotenoids, most notably β-carotene (beta-carotene).
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 .
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. [21] This increased retinyl ester may be due to decreased hepatic uptake of vitamin A and the leaking of esters into the bloodstream from saturated hepatic stellate cells.
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.
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.
Retinoic acid (simplified nomenclature for all-trans-retinoic acid) is a metabolite of vitamin A 1 (all-trans-retinol) that is required for embryonic development, male fertility, regulation of bone growth and immune function. [2]