__NOTOC__ Carotenoid oxygenases are a

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. A ...

s involved in the cleavage of

carotenoid Carotenoids (), also called tetraterpenoids, are yellow, orange, and red organic compound, organic pigments that are produced by plants and algae, as well as several bacteria, and Fungus, fungi. Carotenoids give the characteristic color to pumpki ...

s to produce, for example,

retinol Retinol, also called vitamin A1, is a fat-soluble vitamin in the vitamin A family found in food and used as a dietary supplement. As a supplement it is used to treat and prevent vitamin A deficiency, especially that which results in xerophtha ...

, commonly known as

vitamin A Vitamin A is a fat-soluble vitamin and an essential nutrient for humans. It is a group of organic compounds that includes retinol, retinal (also known as retinaldehyde), retinoic acid, and several provitamin A carotenoids (most notably bet ...

. This family includes an enzyme known as RPE65 which is abundantly expressed in the

retinal pigment epithelium The pigmented layer of retina or retinal pigment epithelium (RPE) is the pigmented cell layer just outside the neurosensory retina that nourishes retinal visual cells, and is firmly attached to the underlying choroid and overlying retinal visual ce ...

where it catalyzed the formation of 11-cis-retinol from all-trans-retinyl esters. RPE65 Active Site

Carotenoids such as beta-carotene,

lycopene Lycopene is an organic compound classified as a tetraterpene and a carotene. Lycopene (from the neo-Latin ''Lycopersicum'', the tomato species) is a bright red carotenoid hydrocarbon found in tomatoes and other red fruits and vegetables. Occu ...

lutein Lutein (;"Lutein"

beta-cryptoxanthin are produced in plants and certain bacteria, algae and fungi, where they function as accessory photosynthetic pigments and as scavengers of oxygen radicals for

photoprotection Photoprotection is the biochemical process that helps organisms cope with molecular damage caused by sunlight. Plants and other oxygenic phototrophs have developed a suite of photoprotective mechanisms to prevent photoinhibition and oxidative stre ...

. They are also essential dietary nutrients in animals. Carotenoid oxygenases cleave a variety of carotenoids into a range of biologically important products, including

apocarotenoid Apocarotenoids are organic compounds which occur widely in living organisms. They are derived from carotenoids by oxidative cleavage, catalyzed by carotenoid oxygenases. Examples include the vitamin A retinoids retinal, retinoic acid, and retinol; a ...

s in plants that function as

hormone A hormone (from the Greek participle , "setting in motion") is a class of signaling molecules in multicellular organisms that are sent to distant organs by complex biological processes to regulate physiology and behavior. Hormones are required ...

s, pigments, flavours, floral scents and defence compounds, and retinoids in animals that function as

vitamin A vitamin is an organic molecule (or a set of molecules closely related chemically, i.e. vitamers) that is an Nutrient#Essential nutrients, essential micronutrient that an organism needs in small quantities for the proper functioning of its ...

chromophore A chromophore is the part of a molecule responsible for its color. The color that is seen by our eyes is the one not absorbed by the reflecting object within a certain wavelength spectrum of visible light. The chromophore is a region in the molec ...

s for

opsin Animal opsins are G-protein-coupled receptors and a group of proteins made light-sensitive via a chromophore, typically retinal. When bound to retinal, opsins become Retinylidene proteins, but are usually still called opsins regardless. Most pro ...

s and signalling molecules. Examples of carotenoid oxygenases include: *

Beta-carotene 15,15'-monooxygenase In enzymology, beta-carotene 15,15'-dioxygenase, () is an enzyme with systematic name ''beta-carotene:oxygen 15,15'-dioxygenase (bond-cleaving)''. In human it is encoded by the BCDO2 gene. This enzyme catalyses the following chemical reaction ...

(BCO1; ) from animals, which cleaves beta-carotene symmetrically at the central double bond to yield two molecules of retinal. * Beta-carotene-9',10'-dioxygenase (BCO2) from animals, which cleaves beta-carotene asymmetrically to apo-10'-beta-carotenal and beta-ionone, the latter being converted to retinoic acid. Lycopene is also oxidatively cleaved. * 9-cis-epoxycarotenoid dioxygenase from plants, which cleaves 9-cis

xanthophyll Xanthophylls (originally phylloxanthins) are yellow pigments that occur widely in nature and form one of two major divisions of the carotenoid group; the other division is formed by the carotenes. The name is from Greek (, "yellow") and (, "l ...

s to

xanthoxin Xanthoxin is an intermediate in the biosynthesis of the plant hormone abscisic acid Abscisic acid (ABA) is a plant hormone. ABA functions in many plant developmental processes, including seed and bud dormancy, the control of organ size and stom ...

, a precursor of the hormone

abscisic acid Abscisic acid (ABA) is a plant hormone. ABA functions in many plant developmental processes, including seed and bud dormancy, the control of organ size and stomatal closure. It is especially important for plants in the response to environmental s ...

. Yellow skin, which is a common phenotype in domestic chicken, is influenced by the accumulation of carotenoids in skin due to absence of beta-carotene dioxygenase 2 (BCDO2) enzyme. Inhibition of expression of BCO2 gene is caused by a regulatory mutation. * Apocarotenoid-15,15'-oxygenase from bacteria and cyanobacteria, which converts beta-apocarotenals rather than beta-carotene into retinal. This protein has a seven-bladed beta-propeller structure. * Retinal pigment epithelium 65 kDa protein (RPE65) from vertebrates which is important for the production of 11-cis retinal during visual opsin regeneration. Members of the family use an iron(II) active center, usually held by four hisitidines.

Human proteins containing this domain

BCO2 BCO may refer to: * Baco Airport, an airport in Ethiopia. * BioCompute Object, a type of computational file built using the BioCompute standard for communicating workflows in high throughput sequencing analysis. * Baseball Confederation of Oceania, ...

; BCO1;

RPE65 Retinal pigment epithelium-specific 65 kDa protein, also known as retinoid isomerohydrolase, is an enzyme of the vertebrate visual cycle that is encoded in humans by the ''RPE65'' gene. RPE65 is expressed in the retinal pigment epithelium (RPE, a ...

;

References

External links

Carotenoid Oxygenase information
{{DEFAULTSORT:Carotenoid Oxygenase Bioindicators Carotenoids Enzymes Protein domains Protein families Peripheral membrane proteins

Human proteins containing this domain

References

Further reading

External links