Reaction Process: WikiPathways:WP716
Vitamin A and carotenoid metabolism related metabolites
find 8 related metabolites which is associated with chemical reaction(pathway) Vitamin A and carotenoid metabolism
Betacarotene ⟶ all-trans Retinal
beta-Carotene
Beta-carotene is a cyclic carotene obtained by dimerisation of all-trans-retinol. A strongly-coloured red-orange pigment abundant in plants and fruit and the most active and important provitamin A carotenoid. It has a role as a biological pigment, a provitamin A, a plant metabolite, a human metabolite, a mouse metabolite, a cofactor, a ferroptosis inhibitor and an antioxidant. It is a cyclic carotene and a carotenoid beta-end derivative. Beta-carotene, with the molecular formula C40H56, belongs to the group of carotenoids consisting of isoprene units. The presence of long chains of conjugated double bonds donates beta-carotene with specific colors. It is the most abundant form of carotenoid and it is a precursor of the vitamin A. Beta-carotene is composed of two retinyl groups. It is an antioxidant that can be found in yellow, orange and green leafy vegetables and fruits. Under the FDA, beta-carotene is considered as a generally recognized as safe substance (GRAS). Beta-Carotene is a natural product found in Epicoccum nigrum, Lonicera japonica, and other organisms with data available. Beta-Carotene is a naturally-occurring retinol (vitamin A) precursor obtained from certain fruits and vegetables with potential antineoplastic and chemopreventive activities. As an anti-oxidant, beta carotene inhibits free-radical damage to DNA. This agent also induces cell differentiation and apoptosis of some tumor cell types, particularly in early stages of tumorigenesis, and enhances immune system activity by stimulating the release of natural killer cells, lymphocytes, and monocytes. (NCI04) beta-Carotene is a metabolite found in or produced by Saccharomyces cerevisiae. A carotenoid that is a precursor of VITAMIN A. Beta carotene is administered to reduce the severity of photosensitivity reactions in patients with erythropoietic protoporphyria (PORPHYRIA, ERYTHROPOIETIC). See also: Lycopene (part of); Broccoli (part of); Lycium barbarum fruit (part of). Beta-Carotene belongs to the class of organic compounds known as carotenes. These are a type of polyunsaturated hydrocarbon molecules containing eight consecutive isoprene units. Carotenes are characterized by the presence of two end-groups (mostly cyclohexene rings, but also cyclopentene rings or acyclic groups) linked by a long branched alkyl chain. Beta-carotene is therefore considered to be an isoprenoid lipid molecule. Beta-carotene is a strongly coloured red-orange pigment abundant in fungi, plants, and fruits. It is synthesized biochemically from eight isoprene units and therefore has 40 carbons. Among the carotenes, beta-carotene is distinguished by having beta-rings at both ends of the molecule. Beta-Carotene is biosynthesized from geranylgeranyl pyrophosphate. It is the most common form of carotene in plants. In nature, Beta-carotene is a precursor (inactive form) to vitamin A. Vitamin A is produed via the action of beta-carotene 15,15-monooxygenase on carotenes. In mammals, carotenoid absorption is restricted to the duodenum of the small intestine and dependent on a class B scavenger receptor (SR-B1) membrane protein, which is also responsible for the absorption of vitamin E. One molecule of beta-carotene can be cleaved by the intestinal enzyme Beta-Beta-carotene 15,15-monooxygenase into two molecules of vitamin A. Beta-Carotene contributes to the orange color of many different fruits and vegetables. Vietnamese gac and crude palm oil are particularly rich sources, as are yellow and orange fruits, such as cantaloupe, mangoes, pumpkin, and papayas, and orange root vegetables such as carrots and sweet potatoes. Excess beta-carotene is predominantly stored in the fat tissues of the body. The most common side effect of excessive beta-carotene consumption is carotenodermia, a physically harmless condition that presents as a conspicuous orange skin tint arising from deposition of the carotenoid in the outermost layer of the epidermis. Yellow food colour, dietary supplement, nutrient, Vitamin A precursor. Nutriceutical with antioxidation props. beta-Carotene is found in many foods, some of which are summer savory, gram bean, sunburst squash (pattypan squash), and other bread product. A cyclic carotene obtained by dimerisation of all-trans-retinol. A strongly-coloured red-orange pigment abundant in plants and fruit and the most active and important provitamin A carotenoid. D - Dermatologicals > D02 - Emollients and protectives > D02B - Protectives against uv-radiation > D02BB - Protectives against uv-radiation for systemic use A - Alimentary tract and metabolism > A11 - Vitamins > A11C - Vitamin a and d, incl. combinations of the two > A11CA - Vitamin a, plain D020011 - Protective Agents > D000975 - Antioxidants > D002338 - Carotenoids D018977 - Micronutrients > D014815 - Vitamins > D000072664 - Provitamins
all-trans-Retinoic acid
all-trans-Retinoic acid is an isomer of retinoic acid, the oxidized form of vitamin A. Retinoic acid functions in determining position along embryonic anterior/posterior axis in chordates. It acts through Hox genes, which ultimately controls anterior/posterior patterning in early developmental stages (PMID:17495912). It is an important regulator of gene expression during growth and development, and in neoplasms. As a drug, all-trans-retinoic acid is known as tretinoin. Tretinoin is derived from maternal vitamin A and is essential for normal growth and embryonic development. An excess of tretinoin can be teratogenic. Tretinoin is used in the treatment of psoriasis, acne vulgaris, and several other skin diseases. It has also been approved for use in promyelocytic leukemia (leukemia, promyelocytic, acute). Retinoic acid is the oxidized form of Vitamin A. It functions in determining position along embryonic anterior/posterior axis in chordates. It acts through Hox genes, which ultimately controls anterior/posterior patterning in early developmental stages (PMID: 17495912). It is an important regulator of gene expression during growth and development, and in neoplasms. Tretinoin, also known as retinoic acid and derived from maternal vitamin A, is essential for normal growth and embryonic development. An excess of tretinoin can be teratogenic. It is used in the treatment of psoriasis; acne vulgaris; and several other skin diseases. It has also been approved for use in promyelocytic leukemia (leukemia, promyelocytic, acute). [HMDB] L - Antineoplastic and immunomodulating agents > L01 - Antineoplastic agents > L01X - Other antineoplastic agents > L01XF - Retinoids for cancer treatment D - Dermatologicals > D10 - Anti-acne preparations > D10A - Anti-acne preparations for topical use > D10AD - Retinoids for topical use in acne C274 - Antineoplastic Agent > C2122 - Cell Differentiating Agent > C1934 - Differentiation Inducer C274 - Antineoplastic Agent > C163758 - Targeted Therapy Agent > C804 - Retinoic Acid Agent Acquisition and generation of the data is financially supported in part by CREST/JST. C308 - Immunotherapeutic Agent > C129820 - Antineoplastic Immunomodulating Agent D020011 - Protective Agents > D000975 - Antioxidants > D002338 - Carotenoids D003879 - Dermatologic Agents > D007641 - Keratolytic Agents D000970 - Antineoplastic Agents Retinoic acid is a metabolite of vitamin A that plays important roles in cell growth, differentiation, and organogenesis. Retinoic acid is a natural agonist of RAR nuclear receptors, with IC50s of 14 nM for RARα/β/γ. Retinoic acid bind to PPARβ/δ with Kd of 17 nM. Retinoic acid acts as an inhibitor of transcription factor Nrf2 through activation of retinoic acid receptor alpha. Retinoic acid is a metabolite of vitamin A that plays important roles in cell growth, differentiation, and organogenesis. Retinoic acid is a natural agonist of RAR nuclear receptors, with IC50s of 14 nM for RARα/β/γ. Retinoic acid bind to PPARβ/δ with Kd of 17 nM. Retinoic acid acts as an inhibitor of transcription factor Nrf2 through activation of retinoic acid receptor alpha. Retinoic acid is a metabolite of vitamin A that plays important roles in cell growth, differentiation, and organogenesis. Retinoic acid is a natural agonist of RAR nuclear receptors, with IC50s of 14 nM for RARα/β/γ. Retinoic acid bind to PPARβ/δ with Kd of 17 nM. Retinoic acid acts as an inhibitor of transcription factor Nrf2 through activation of retinoic acid receptor alpha.
Retinal
A carotenoid constituent of visual pigments. It is the oxidized form of retinol which functions as the active component of the visual cycle. It is bound to the protein opsin forming the complex rhodopsin. When stimulated by visible light, the retinal component of the rhodopsin complex undergoes isomerization at the 11-position of the double bond to the cis-form; this is reversed in "dark" reactions to return to the native trans-configuration. [HMDB]. Retinal is found in many foods, some of which are flaxseed, pepper (c. baccatum), climbing bean, and other soy product. Retinal is a carotenoid constituent of visual pigments. It is the oxidized form of retinol which functions as the active component of the visual cycle. It is bound to the protein opsin forming the complex rhodopsin. When stimulated by visible light, the retinal component of the rhodopsin complex undergoes isomerization at the 11-position of the double bond to the cis-form; this is reversed in "dark" reactions to return to the native trans-configuration. D020011 - Protective Agents > D000975 - Antioxidants > D002338 - Carotenoids CONFIDENCE standard compound; INTERNAL_ID 142
Retinol(Vitamin A)
Vitamin A (retinol) is a yellow fat-soluble, antioxidant vitamin important in vision and bone growth. It belongs to the family of chemical compounds known as retinoids. Retinol is ingested in a precursor form; animal sources (milk and eggs) contain retinyl esters, whereas plants (carrots, spinach) contain pro-vitamin A carotenoids. Hydrolysis of retinyl esters results in retinol while pro-vitamin A carotenoids can be cleaved to produce retinal. Retinal, also known as retinaldehyde, can be reversibly reduced to produce retinol or it can be irreversibly oxidized to produce retinoic acid. Retinol and derivatives of retinol that play an essential role in metabolic functioning of the retina, the growth of and differentiation of epithelial tissue, the growth of bone, reproduction, and the immune response. Dietary vitamin A is derived from a variety of carotenoids found in plants. It is enriched in the liver, egg yolks, and the fat component of dairy products. Retinyl esters from animal-sourced foods (or synthesized for dietary supplements for humans and domesticated animals) are acted upon by retinyl ester hydrolases in the lumen of the small intestine to release free retinol. Retinol enters intestinal absorptive cells by passive diffusion. Absorption efficiency is in the range of 70 to 90\%. Humans are at risk for acute or chronic vitamin A toxicity because there are no mechanisms to suppress absorption or excrete the excess in urine.[5] Within the cell, retinol is there bound to retinol binding protein 2 (RBP2). It is then enzymatically re-esterified by the action of lecithin retinol acyltransferase and incorporated into chylomicrons that are secreted into the lymphatic system. Unlike retinol, β-carotene is taken up by enterocytes by the membrane transporter protein scavenger receptor B1 (SCARB1). The protein is upregulated in times of vitamin A deficiency. If vitamin A status is in the normal range, SCARB1 is downregulated, reducing absorption.[6] Also downregulated is the enzyme beta-carotene 15,15'-dioxygenase (formerly known as beta-carotene 15,15'-monooxygenase) coded for by the BCMO1 gene, responsible for symmetrically cleaving β-carotene into retinal.[8] Absorbed β-carotene is either incorporated as such into chylomicrons or first converted to retinal and then retinol, bound to RBP2. After a meal, roughly two-thirds of the chylomicrons are taken up by the liver with the remainder delivered to peripheral tissues. Peripheral tissues also can convert chylomicron β-carotene to retinol.[6][15] The capacity to store retinol in the liver means that well-nourished humans can go months on a vitamin A deficient diet without manifesting signs and symptoms of deficiency. Two liver cell types are responsible for storage and release: hepatocytes and hepatic stellate cells (HSCs). Hepatocytes take up the lipid-rich chylomicrons, bind retinol to retinol-binding protein 4 (RBP4), and transfer the retinol-RBP4 to HSCs for storage in lipid droplets as retinyl esters. Mobilization reverses the process: retinyl ester hydrolase releases free retinol which is transferred to hepatocytes, bound to RBP4, and put into blood circulation. Other than either after a meal or when consumption of large amounts exceeds liver storage capacity, more than 95\% of retinol in circulation is bound to RBP4.[15] Vitamin A is a fat-soluble vitamin, hence an essential nutrient. The term "vitamin A" encompasses a group of chemically related organic compounds that includes retinol, retinal (also known as retinaldehyde), retinoic acid, and several provitamin (precursor) carotenoids, most notably beta-carotene.[3][4][5][6] Vitamin A has multiple functions: essential in embryo development for growth, maintaining the immune system, and healthy vision, where it combines with the protein opsin to form rhodopsin – the light-absorbing molecule necessary for both low-light (scotopic vision) and color vision.[7] Vitamin A occurs as two principal forms in foods: A) retinol, found in animal-sourced foods, either as retinol or bound to a fatty acid to become a retinyl ester, and B) the carotenoids alpha-carotene, β-carotene, gamma-carotene, and the xanthophyll beta-cryptoxanthin (all of which contain β-ionone rings) that function as provitamin A in herbivore and omnivore animals which possess the enzymes that cleave and convert provitamin carotenoids to retinal and then to retinol.[8] Some carnivore species lack this enzyme. The other carotenoids have no vitamin activity.[6] Dietary retinol is absorbed from the digestive tract via passive diffusion. Unlike retinol, β-carotene is taken up by enterocytes by the membrane transporter protein scavenger receptor B1 (SCARB1), which is upregulated in times of vitamin A deficiency.[6] Storage of retinol is in lipid droplets in the liver. A high capacity for long-term storage of retinol means that well-nourished humans can go months on a vitamin A- and β-carotene-deficient diet, while maintaining blood levels in the normal range.[4] Only when the liver stores are nearly depleted will signs and symptoms of deficiency show.[4] Retinol is reversibly converted to retinal, then irreversibly to retinoic acid, which activates hundreds of genes.[9] Vitamin A deficiency is common in developing countries, especially in Sub-Saharan Africa and Southeast Asia. Deficiency can occur at any age but is most common in pre-school age children and pregnant women, the latter due to a need to transfer retinol to the fetus. Vitamin A deficiency is estimated to affect approximately one-third of children under the age of five around the world, resulting in hundreds of thousands of cases of blindness and deaths from childhood diseases because of immune system failure.[10] Reversible night blindness is an early indicator of low vitamin A status. Plasma retinol is used as a biomarker to confirm vitamin A deficiency. Breast milk retinol can indicate a deficiency in nursing mothers. Neither of these measures indicates the status of liver reserves.[6] The European Union and various countries have set recommendations for dietary intake, and upper limits for safe intake. Vitamin A toxicity also referred to as hypervitaminosis A, occurs when there is too much vitamin A accumulating in the body. Symptoms may include nervous system effects, liver abnormalities, fatigue, muscle weakness, bone and skin changes, and others. The adverse effects of both acute and chronic toxicity are reversed after consumption of high dose supplements is stopped.[6]
All-trans-13,14-dihydroretinol
All-trans-13,14-dihydroretinol is involved in the retinol metabolism pathway. In this pathway, all-trans-13,14-dihydroretinol and an acceptor molecule is reversibly converted to retinol (vitamin A) plus reduced acceptor via the enzyme all-trans-retinol 13,14-reductase (EC 1.3.99.23). (KEGG) [HMDB] All-trans-13,14-dihydroretinol is involved in the retinol metabolism pathway. In this pathway, all-trans-13,14-dihydroretinol and an acceptor molecule is reversibly converted to retinol (vitamin A) plus reduced acceptor via the enzyme all-trans-retinol 13,14-reductase (EC 1.3.99.23). (KEGG). D020011 - Protective Agents > D000975 - Antioxidants > D002338 - Carotenoids
4-Ketoretinoic acid
D020011 - Protective Agents > D000975 - Antioxidants > D002338 - Carotenoids all-trans-4-Oxoretinoic acid, an active metabolite of vitamin A, induces gene transcription via binding to nuclear retinoic acid receptors (RARs).
9-cis-Retinol
9-cis-retinol is a retinoid. Retinoids (vitamin A and its analogs) are essential dietary substances that are needed by mammals for reproduction, normal embryogenesis, growth, vision, and maintaining normal cellular differentiation and the integrity of the immune system. Within cells, retinoids regulate gene transcription acting through ligand-dependent transcription factors, the retinoic acid receptors (RARs), and the retinoid X receptors (RXRs). All-trans-retinoic acid binds only to RARs with high affinity, whereas its 9-cis isomer binds with high affinity to both RARs and RXRs. The actions of all-trans- and 9-cis-retinoic acid in regulating cellular responses are distinct and not interchangeable. (PMID: 9115228). Constituent of cod liver oil
9-cis-Retinal
In vivo, 9-cis-retinal is formed through oxidation of 9-cis-retinol by cis-retinol dehydrogenase (cRDH). (PMID:15572038). The generation of retinoic acid from retinol is a two-step reaction, with the rate-limiting step being the oxidation of retinol into the intermediate retinaldehyde. Two classes of. unrelated enzymes have been implicated in the oxidation of retinol, the classical cytosolic medium chain alcohol dehydrogenases and recently identified microsomal members of the short chain alcohol dehydrogenase reductase (SDR) superfamily. Further oxidation of the retinaldehyde to the retinoic acid is believed to be catalyzed by several cytosolic aldehyde dehydrogenases. Retinoids are micronutrients required to maintain and promote health of vertebrates. They act physiologically by participating in the visual cycle, in regulating cell differentiation, in embryonic development (PMID:10893430), in maintaining normal reproduction, and in the immune response (PMID:8882153). In non-ocular tissues, the effects of retinoids within the body are mediated through retinoic acid receptors (RARs) and retinoid X receptors (RXRs), which act to regulate gene expression as ligand-dependent transcription factors. The naturally occurring ligands for these nuclear receptors are thought to be all-trans-retinoic acid for RARs and 9-cis-retinoic acid for RXRs (PMID:10322133). While many details of the molecular actions of the RARs and RXRs in regulating gene transcription are understood (PMID:10418975), tissue-specific synthetic pathway(s) of their ligands has not been adequately defined. Nevertheless, the therapeutic efficacy of retinoids, including 9-cis-retinoic acid, is well established in both tissue culture and animal models of breast cancer (PMID:8825126, PMID:12743994). In vivo, 9-cis-retinal is formed through oxidation of 9-cis-retinol by cis-retinol dehydrogenase (cRDH). (PMID: 15572038). The generation of retinoic acid from retinol is a two-step reaction, with the rate-limiting step being the oxidation of retinol into the intermediate retinaldehyde. Two classes of D020011 - Protective Agents > D000975 - Antioxidants > D002338 - Carotenoids