Carotenoids are yellow, orange, and red organic pigments that are produced by plants and algae, as well as several bacteria, archaea, and fungi. Carotenoids give the characteristic color to pumpkins, carrots, parsnips, corn, tomatoes, canaries, flamingos, salmon, lobster, shrimp, and daffodils. Over 1,100 identified carotenoids can be further categorized into two classes – xanthophylls and carotenes.
β-Carotene (beta-carotene) is an organic, strongly coloured red-orange pigment abundant in fungi, plants, and fruits. It is a member of the carotenes, which are terpenoids (isoprenoids), synthesized biochemically from eight isoprene units and thus having 40 carbons. Among the carotenes, β-carotene is distinguished by having beta-rings at both ends of the molecule. β-Carotene is biosynthesized from geranylgeranyl pyrophosphate.
Xanthophylls 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: xanthos (ξανθός), meaning "yellow", and phyllon (φύλλον), meaning "leaf"), due to their formation of the yellow band seen in early chromatography of leaf pigments.
The ionones, from greek ἴον ion "violet", are a series of closely related chemical substances that are part of a group of compounds known as rose ketones, which also includes damascones and damascenones. Ionones are aroma compounds found in a variety of essential oils, including rose oil. β-Ionone is a significant contributor to the aroma of roses, despite its relatively low concentration, and is an important fragrance chemical used in perfumery. The ionones are derived from the degradation of carotenoids.
Lutein is a xanthophyll and one of 600 known naturally occurring carotenoids. Lutein is synthesized only by plants, and like other xanthophylls is found in high quantities in green leafy vegetables such as spinach, kale and yellow carrots. In green plants, xanthophylls act to modulate light energy and serve as non-photochemical quenching agents to deal with triplet chlorophyll, an excited form of chlorophyll which is overproduced at very high light levels during photosynthesis. See xanthophyll cycle for this topic.
Zeaxanthin is one of the most common carotenoids in nature, and is used in the xanthophyll cycle. Synthesized in plants and some micro-organisms, it is the pigment that gives paprika, corn, saffron, goji (wolfberries), and many other plants and microbes their characteristic color.
Carotenoid oxygenases are a family of enzymes involved in the cleavage of carotenoids to produce, for example, retinol, commonly known as vitamin A. This family includes an enzyme known as RPE65 which is abundantly expressed in the retinal pigment epithelium where it catalyzed the formation of 11-cis-retinol from all-trans-retinyl esters.
CRT is the gene cluster responsible for the biosynthesis of carotenoids. Those genes are found in eubacteria, in algae and are cryptic in Streptomyces griseus.
In enzymology, beta-carotene 15,15'-dioxygenase, (EC 1.13.11.63) 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
In enzymology, a 7,8-dihydroxykynurenate 8,8a-dioxygenase (EC 1.13.11.10) is an enzyme that catalyzes the chemical reaction
Dioxygenases are oxidoreductase enzymes. Aerobic life, from simple single-celled bacteria species to complex eukaryotic organisms, has evolved to depend on the oxidizing power of dioxygen in various metabolic pathways. From energetic adenosine triphosphate (ATP) generation to xenobiotic degradation, the use of dioxygen as a biological oxidant is widespread and varied in the exact mechanism of its use. Enzymes employ many different schemes to use dioxygen, and this largely depends on the substrate and reaction at hand.
Damascenones are a series of closely related chemical compounds that are components of a variety of essential oils. The damascenones belong to a family of chemicals known as rose ketones, which also includes damascones and ionones. beta-Damascenone is a major contributor to the aroma of roses, despite its very low concentration, and is an important fragrance chemical used in perfumery.
Phaseic acid is a terpenoid catabolite of abscisic acid. Like abscisic acid, it is a plant hormone associated with photosynthesis arrest and abscission.
Carotenoid isomerooxygenase (EC 1.13.11.65, ninaB (gene)) is an enzyme with systematic name zeaxanthin:oxygen 15,15'-oxidoreductase (bond-cleaving, cis-isomerizing). This enzyme catalyses the following chemical reaction
8'-apo-beta-carotenoid 14',13'-cleaving dioxygenase (EC 1.13.11.67) is an enzyme with systematic name 8'-apo-beta-carotenol:O2 oxidoreductase (14',13'-cleaving). This enzyme catalyses the following chemical reaction
9-cis-beta-carotene 9',10'-cleaving dioxygenase (EC 1.13.11.68, CCD7 (gene), MAX3 (gene), NCED7 (gene)) is an enzyme with systematic name 9-cis-beta-carotene:O2 oxidoreductase (9',10'-cleaving). This enzyme catalyses the following chemical reaction
Carlactone synthase (EC 1.13.11.69, CCD8 (gene), MAX4 (gene), NCED8 (gene)) is an enzyme with systematic name 9-cis-10'-apo-beta-carotenal:O2 oxidoreductase (14,15-cleaving, carlactone-forming). This enzyme catalyses the following chemical reaction
All-trans-10'-apo-beta-carotenal 13,14-cleaving dioxygenase (EC 1.13.11.70, CCD8 (gene), MAX4 (gene), NCED8 (gene)) is an enzyme with systematic name all-trans-10'-apo-beta-carotenal:O2 oxidoreductase (13,14-cleaving). This enzyme catalyses the following chemical reaction
Carotenoid-9',10'-cleaving dioxygenase (EC 1.13.11.71, BCO2 (gene), beta-carotene 9',10'-monooxygenase (misleading)) is an enzyme with systematic name all-trans-beta-carotene:O2 oxidoreductase (9',10'-cleaving). This enzyme catalyses the following chemical reaction
meso-Zeaxanthin (3R,3´S-Zeaxanthin) is a xanthophyll carotenoid, as it contains oxygen and hydrocarbons, and is one of the three stereoisomers of zeaxanthin. Of the three stereoisomers, meso-zeaxanthin is the second most abundant in nature after 3R,3´R-zeaxanthin, which is produced by plants and algae. To date, meso-zeaxanthin has been identified in specific tissues of marine organisms and in the macula lutea, also known as the "yellow spot", of the human retina.
