Showing metabocard for Vitamin A (BMDB0000305)

General function:

Energy production and conversion

Specific function:

Can convert/oxidize retinaldehyde to retinoic acid. Binds free retinal and cellular retinol-binding protein-bound retinal. May have a broader specificity and oxidize other aldehydes in vivo.

Gene Name:

ALDH1A1

Uniprot ID:

P48644

Molecular weight:

54806.0

Reactions

General function:

Lipid transport and metabolism

Specific function:

NAD-dependent oxidoreductase with broad substrate specificity that shows both oxidative and reductive activity (in vitro). Has 17-beta-hydroxysteroid dehydrogenase activity towards various steroids (in vitro). Converts 5-alpha-androstan-3-alpha,17-beta-diol to androsterone and estradiol to estrone (in vitro). Has 3-alpha-hydroxysteroid dehydrogenase activity towards androsterone (in vitro). Has retinol dehydrogenase activity towards all-trans-retinol (in vitro). Can convert androsterone to epi-androsterone. Androsterone is first oxidized to 5-alpha-androstane-3,17-dione and then reduced to epi-andosterone. Can act on both C-19 and C-21 3-alpha-hydroxysteroids (By similarity).

Gene Name:

HSD17B6

Uniprot ID:

Q3T001

Molecular weight:

36198.0

General function:

Lipid transport and metabolism

Specific function:

Retinol dehydrogenase with a clear preference for NADP. Converts all-trans-retinal to all-trans-retinol. May play a role in the regeneration of visual pigment at high light intensity.

Gene Name:

RDH8

Uniprot ID:

Q9N126

Molecular weight:

33956.0

General function:

Involved in phosphatidylcholine-retinol O-acyltransfera

Specific function:

Transfers the acyl group from the sn-1 position of phosphatidylcholine to all-trans retinol, producing all-trans retinyl esters (PubMed:9920938, PubMed:2722792). Retinyl esters are storage forms of vitamin A (Probable). LRAT plays a critical role in vision (Probable). It provides the all-trans retinyl ester substrates for the isomerohydrolase which processes the esters into 11-cis-retinol in the retinal pigment epithelium; due to a membrane-associated alcohol dehydrogenase, 11 cis-retinol is oxidized and converted into 11-cis-retinaldehyde which is the chromophore for rhodopsin and the cone photopigments (Probable). Required for the survival of cone photoreceptors and correct rod photoreceptor cell morphology (By similarity).

Gene Name:

LRAT

Uniprot ID:

Q9BGL2

Molecular weight:

25701.0

General function:

Lipid transport and metabolism

Specific function:

Catalyzes the oxidation of cis-isomers of retinol, including 11-cis-, 9-cis-, and 13-cis-retinol in an NAD-dependent manner (PubMed:7544779, PubMed:7836368, PubMed:9654122). Has no activity towards all-trans retinal (PubMed:9654122). Plays a significant role in 11-cis retinol oxidation in the retinal pigment epithelium cells (RPE) (By similarity). Also recognizes steroids (androsterone, androstanediol) as its substrates (By similarity).

Gene Name:

RDH5

Uniprot ID:

Q27979

Molecular weight:

35037.0

General function:

Lipid transport and metabolism

Specific function:

Retinol dehydrogenase with a clear preference for NADP. Converts all-trans-retinol to all-trans-retinal. Has no detectable activity towards 11-cis-retinol, 9-cis-retinol and 13-cis-retinol (By similarity).

Gene Name:

RDH10

Uniprot ID:

Q8HZT6

Molecular weight:

38087.0

General function:

Lipid transport and metabolism

Specific function:

Retinoids dehydrogenase/reductase with a clear preference for NADP. Displays high activity towards 9-cis, 11-cis and all-trans-retinal. Shows very weak activity towards 13-cis-retinol. Also exhibits activity, albeit with lower affinity than for retinaldehydes, towards lipid peroxidation products (C9 aldehydes) such as 4-hydroxynonenal and trans-2-nonenal. May play an important function in photoreceptor cells to detoxify 4-hydroxynonenal and potentially other toxic aldehyde products resulting from lipid peroxidation. Has no dehydrogenase activity towards steroids.

Gene Name:

RDH12

Uniprot ID:

P59837

Molecular weight:

35171.0

Reactions

General function:

Secondary metabolites biosynthesis, transport and catabolism

Specific function:

Critical isomerohydrolase in the retinoid cycle involved in regeneration of 11-cis-retinal, the chromophore of rod and cone opsins. Catalyzes the cleavage and isomerization of all-trans-retinyl fatty acid esters to 11-cis-retinol which is further oxidized by 11-cis retinol dehydrogenase to 11-cis-retinal for use as visual chromophore (PubMed:16096063, PubMed:19805034, PubMed:20100834). Essential for the production of 11-cis retinal for both rod and cone photoreceptors. Also capable of catalyzing the isomerization of lutein to meso-zeaxanthin an eye-specific carotenoid (By similarity). The soluble form binds vitamin A (all-trans-retinol), making it available for LRAT processing to all-trans-retinyl ester. The membrane form, palmitoylated by LRAT, binds all-trans-retinyl esters, making them available for IMH (isomerohydrolase) processing to all-cis-retinol. The soluble form is regenerated by transferring its palmitoyl groups onto 11-cis-retinol, a reaction catalyzed by LRAT (PubMed:15186777).

Gene Name:

RPE65

Uniprot ID:

Q28175

Molecular weight:

60944.0

General function:

Involved in retinal binding

Specific function:

Cytosolic CRABPs may regulate the access of retinoic acid to the nuclear retinoic acid receptors.

Gene Name:

CRABP1

Uniprot ID:

P62964

Molecular weight:

15592.0

General function:

Involved in retinal binding

Specific function:

Transports retinoic acid to the nucleus. Regulates the access of retinoic acid to the nuclear retinoic acid receptors (By similarity).

Gene Name:

CRABP2

Uniprot ID:

Q5PXY7

Molecular weight:

15735.0

General function:

Involved in retinol binding

Specific function:

Primary component of whey, it binds retinol and is probably involved in the transport of that molecule.

Gene Name:

LGB

Uniprot ID:

P02754

Molecular weight:

19883.0

General function:

Cell wall/membrane/envelope biogenesis

Specific function:

Not Available

Gene Name:

Not Available

Uniprot ID:

Q28129

Molecular weight:

39621.0

General function:

Involved in retinol binding

Specific function:

Soluble retinoid carrier essential the proper function of both rod and cone photoreceptors. Participates in the regeneration of active 11-cis-retinol and 11-cis-retinaldehyde, from the inactive 11-trans products of the rhodopsin photocycle and in the de novo synthesis of these retinoids from 11-trans metabolic precursors. The cycling of retinoids between photoreceptor and adjacent pigment epithelium cells is known as the 'visual cycle'.

Gene Name:

RLBP1

Uniprot ID:

P10123

Molecular weight:

36505.0

General function:

Involved in retinal binding

Specific function:

Intracellular transport of retinol.

Gene Name:

RBP5

Uniprot ID:

P82708

Molecular weight:

15962.0

General function:

Involved in retinal binding

Specific function:

Cytoplasmic retinol-binding protein (PubMed:7744071). Accepts retinol from the transport protein STRA6, and thereby contributes to retinol uptake, storage and retinoid homeostasis.

Gene Name:

RBP1

Uniprot ID:

P02694

Molecular weight:

15823.0

General function:

Cell wall/membrane/envelope biogenesis

Specific function:

IRBP shuttles 11-cis and all trans retinoids between the retinol isomerase in the pigment epithelium and the visual pigments in the photoreceptor cells of the retina.

Gene Name:

RBP3

Uniprot ID:

P12661

Molecular weight:

139698.0

General function:

Not Available

Specific function:

Functions as retinol transporter. Accepts all-trans retinol from the extracellular retinol-binding protein RBP4, facilitates retinol transport across the cell membrane, and then transfers retinol to the cytoplasmic retinol-binding protein RBP1 (PubMed:17255476, PubMed:18419130). Retinol uptake is enhanced by LRAT, an enzyme that converts retinol to all-trans retinyl esters, the storage forms of vitamin A. Contributes to the activation of a signaling cascade that depends on retinol transport and LRAT-dependent generation of retinol metabolites that then trigger activation of JAK2 and its target STAT5, and ultimately increase the expression of SOCS3 and inhibit cellular responses to insulin. Important for the homeostasis of vitamin A and its derivatives, such as retinoic acid. STRA6-mediated transport is particularly important in the eye, and under conditions of dietary vitamin A deficiency. Does not transport retinoic acid (By similarity).

Gene Name:

STRA6

Uniprot ID:

Q0V8E7

Molecular weight:

73762.0

General function:

Involved in retinal binding

Specific function:

Retinol-binding protein that mediates retinol transport in blood plasma. Delivers retinol from the liver stores to the peripheral tissues. Transfers the bound all-trans retinol to STRA6, that then facilitates retinol transport across the cell membrane.

Gene Name:

RBP4

Uniprot ID:

P18902

Molecular weight:

21069.0

General function:

Involved in lipid binding

Specific function:

Not Available

Gene Name:

RBP1

Uniprot ID:

Q58DG0

Molecular weight:

11488.0

General function:

Not Available

Specific function:

Catalyzes the terminal and only committed step in triacylglycerol synthesis by using diacylglycerol and fatty acyl CoA as substrates. In contrast to DGAT2 it is not essential for survival. May be involved in VLDL (very low density lipoprotein) assembly. Functions as the major acyl-CoA retinol acyltransferase (ARAT) in the skin, where it acts to maintain retinoid homeostasis and prevent retinoid toxicity leading to skin and hair disorders. In liver, plays a role in esterifying exogenous fatty acids to glycerol.

Gene Name:

DGAT1

Uniprot ID:

Q8MK44

Molecular weight:

55602.0

Reactions

General function:

Not Available

Specific function:

Catalyzes the initial step in triglyceride hydrolysis in adipocyte and non-adipocyte lipid droplets. Also has acylglycerol transacylase activity. May act coordinately with LIPE/HLS within the lipolytic cascade. Regulates adiposome size and may be involved in the degradation of adiposomes. May play an important role in energy homeostasis. May play a role in the response of the organism to starvation, enhancing hydrolysis of triglycerides and providing free fatty acids to other tissues to be oxidized in situations of energy depletion.

Gene Name:

PNPLA2

Uniprot ID:

Q2KI18

Molecular weight:

53417.0

Reactions

General function:

Not Available

Specific function:

Involved in the metabolism of retinoic acid (RA), rendering this classical morphogen inactive through oxidation. Involved in the specific inactivation of all-trans-retinoic acid (all-trans-RA), with a preference for the following substrates: all-trans-RA > 9-cis-RA > 13-cis-RA. Generates several hydroxylated forms of RA, including 4-OH-RA, 4-oxo-RA, and 18-OH-RA. Essential for postnatal survival. Plays a central role in germ cell development: acts by degrading RA in the developing testis, preventing STRA8 expression, thereby leading to delay of meiosis. Required for the maintenance of the undifferentiated state of male germ cells during embryonic development in Sertoli cells, inducing arrest in G0 phase of the cell cycle and preventing meiotic entry. Plays a role in skeletal development, both at the level of patterning and in the ossification of bone and the establishment of some synovial joints (By similarity).

Gene Name:

CYP26B1

Uniprot ID:

E1BHJ4

Molecular weight:

57414.0

Reactions

General function:

Not Available

Specific function:

Not Available

Gene Name:

RETSAT

Uniprot ID:

E1BDK9

Molecular weight:

66777.0

Reactions