Biosynthesis of carotenoids

Carotenoids play a key role in human diet by virtue of their metabolism to vitamin A (retinol, 61). As the prosthetic group associated with the light-harvesting pigment rhodopsin, retinol is critically involved in visual processes. It is also a participant in growth and development processes, so vitamin A deficiency, which is estimated to inflict 124 million children worldwide, can have serious consequences for long-term health (Beyer et al. 2002). The antioxidant properties of carotenoids have also been implicated in the protection against heart disease and cancer (Fraser and Bramley 2004). 

The predominant product of PSY in plants is the counter-intuitively numbered 15-cis-phytoene (8). Phytoene is dehydrogenated in a series of enzymatic steps to yield lycopene 

IPP and DMAPP obtained from the isoprenoid pathways can be condensed into the Cj o molecule geranyl pyrophosphate (GPP), which is then converted to the Cj5 compound farnesyl pyrophosphate (FPP) with the addition of an isoprene 

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Biosynthesis of carotenoids with genetically engineered hosts . Patent PCT/US91/ 01458. 

Carotenoids are predominantly synthesized in nature by photosynthetic plants, algae, bacteria, and some fungi. - Animals can metabolize carotenoids in a characteristic manner, but they are not able to synthesize carotenoids. The total global biosynthesis of carotenoids is estimated to be in excess of 100 million tons per year. ... 

For the sake of study, the biosynthesis of carotenoid plant pigments can be divided into parts involving enzymes and their associated activities as listed in Table 5.3.1 and further detailed in Figure 5.3.1 through Figure 5.3.4. Some of the parts have common enzymatic mechanisms and may also be in distinct subcellular compartments such as cytoplasm, endoplasmic reticulum, or plastid thylakoid. 

Buckner, B. et al.. Cloning of the yl locus of maize, a gene involved in the biosynthesis of carotenoids, Plant Cell 2, 867, 1990. 

Britton G. 1988. Biosynthesis of carotenoids. In Goodwin TR, editor. Plant Pigments. London Academic Press, pp. 133—182. 

Tran TLH and Raymundo LC. 1999. Biosynthesis of carotenoids in bittermelon at high temperature. Phytochemistry 52 275—280. 

Deli J, Molnar P, Toth G (2001) Carotenoid composition in the fruits of red paprika (Capsicum annuum var. lycopersiciforme rubrum) during ripening biosynthesis of carotenoids in red paprika. J Agric Food Chem 49 1517-1523... 

The molecular target site of triketone herbicides is the enzyme -hydroxyphenylpyruvate dioxygenase (HPPD). Inhibition of this enzyme disrupts the biosynthesis of carotenoids and causes a bleaching (loss of chlorophyll) effect on the foliage similar to that observed with inhibitors ofphytoene desaturase (e.g. norflurazon). However, the mechanism of action of HPPD inhibitors is different. Inhibtion of HPPD stops the synthesis of homogen tisate (HGA), which is a key precursor of the 8 different tocochromanols (tocopherols and tocotrienols) and prenyl quinones. In the absence of prenylquinone plastoquinone, phytoene desaturase activity is interrupted. The bleaching of the green tissues ensues as if these compounds inhibited phytoene desaturase. 

Goodwin TW, Biosynthesis of carotenoids An overview, Method Enzymol 214 330-340(1992). 

Liaaen-Jensen, S., Cohen-Bazire, G. and Stanier, R.Y. 1961. Biosynthesis of carotenoids in purple bacteria A reevaluation based on considerations of chemical structure. Nature (London), 192,1168-1172. 

The effect of temperature on photo-induced biosynthesis of carotenoids in Neuro-spora crassa has been studied368 and the ability of redox dyes to act as artificial photoreceptors in a similar system has been investigated.369... 

Carotenoids are regarded as part of the aroma potential of grape, as they are the biogenetic precursors of C13-norisoprenoids, a chemical family with many powerful odorants, which are mainly found as glycoconjugates in grape (Baumes et al. 2002 Enzell 1985 Mathieu et al. 2005 Winterhalter 1993). Sunshine favors the biosynthesis of carotenoids in the berry, from the first stage of fruit formation... 

Low O2 generally delays or Inhibits the synthesis of lycopene, 11-carotene, and xanthophylls In tomato fruit (31.321. In sweet pepper, high COg delayed development of red color equally whether combined with 21% or 3% 02 (33). C2H4 Is known to accelerate the biosynthesis of carotenoids (34). 

Fruits with a marked de novo biosynthesis of carotenoids, referred to as carotenogenic fraits (i.e., tomato, red pepper, orange, persimmon, etc.). 

During ripening of non-climacteric fruits like citrus, the process of colour change is named degreening and the natural loss of chlorophylls, accumulated into the chromoplasts of the epidermis (flavedo) and vesicles, and the concomitant manifestation and new biosynthesis of carotenoids, generally occurs very slowly (Eaks 1977). 

Biosynthesis and Metabolism.—Several reviews include a consideration of the biosynthesis of carotenoids in plants or algae, and the biosynthesis of C30... 

The biosynthesis of carotenoids in plants has been reviewed extensively in recent years and is only briefly described here (Britton, 1988 Bartley and Scolnik, 1994 Sandmann, 1994). The committed step to carotenoid synthesis is the formation of the first compound phytoene by the head-to-head condensation of two molecules of GGDP by phytoene synthase. Phytoene is subjected to a series of four sequential desaturation reactions, by two separate enzymes to yield lycopene, which has eleven conjugated double bonds. Lycopene is then cyclized to /3-carotene by two /3-cyclizations or to a-carotene... 

Biosynthesis of Carotenoid Giucoside and its Fatty Acid Ester... 

Schmidt K (1978) Biosynthesis of carotenoids. In Clayton RK and Sistrom WR (eds) The Photosynthetic Bacteria, pp 729-750. Prenum Press, New York... 

Scolnik PA, Walker MA and Marrs BL (1980) Biosynthesis of carotenoids derived from neurosporene in Rhodopseudomonas capsulata. J Biol Chem 255 2427-2432... 

Rhee KH, Morris EP, Zheleva D, Hankamer B, Kiihlbrandt W and Barber J (1997) Two dimensional structure of plant Photosystem II at 8 A resolution. Nature 389 522-526 Rock CD and Zeevaart JAD (1991) The aba mutant of Arabidopsis thaliana is impaired in epoxy-carotenoid biosynthesis. Proc Natl Acad Sci USA 88 7496-7499 Rock CD, Bowlby NR, Hoffmann-Benning S and Zeevaart JAD (1992) The aba mutant of Arabidopsis thaliana (L) Heynh. has reduced chlorophyll fluorescence yields and reduced thylakoid stacking. Plant Physiol 100 1796-1801 Romer S, Humbeck K and Senger H (1990) Relationship between biosynthesis of carotenoids and increasing complexity of Photosystem I in mutant C-6D of Scenedesmus obliquus. Planta 182 216-222... 

Thorough biochemical analysis of carotenoid biosynthesis, classical genetics, and more recently molecular genetics resulted in the elucidation of the main routes for the synthesis of acyclic and cyclic carotenoids at a molecular level (Sandmann 2001). Little is known, however, about the biosynthesis of carotenoids containing additional modifications of the end groups, the polyene chain, the methyl groups, or molecular rearrangements that contribute to the tremendous structural diversity of carotenoids. At present, hundreds of individual carotenoids have been characterized (Britton et al. 1998), and novel carotenoids continue to be isolated. All carotenoids are derived from the isoprenoid or terpenoid pathway. 

The I.U.P.A.C.-I.U.B. tentative nomenclature for carotenoids has been widely published. Recent progress in carotenoid and related fields has appeared in the proceedings of the Phytochemical Society Symposium held in Liverpool in 1970. In particular, advances in carotenoid chemistry are surveyed by Liaaen-Jensen the distribution and taxonomic significance of algal carotenoids by Goodwin and studies on abscisic acid by Milborrow. A symposium on sporopollenin has been published which includes a discussion on its possible origin from carotenoids. The properties of yeast pigments are summarized in a chapter written by Chichester and co-workers." The obituary of Professor P. Karrer outlines some of his many contributions to carotenoid chemistry. Advances in the biosynthesis of carotenoids and polyterpenoids are dealt with in the next chapter. 

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