Xanthophyll biosynthesis

BOUVIER F, D HARLINGUE A, HUGUENEY P, MARIN E, MARION-POLL A and CAMARA B (1996) Xanthophyll biosynthesis cloning, expression, functional reconstitution and regulation of 3-cyclohexenyl carotenoid epoxidase from pepper Capsicum annuum) , J Biol Chem, 271, 28861-7. 

BOUVIER F, KELLER Y, d harlingue A and CAMARA B (1998) Xanthophyll biosynthesis molecular and functional characterisation of carotenoid hydroxylases from pepper fruits Capsicum annuum L.) , Biochim Biophys Acta, 1391, 320-28. 

Bouvier, F. et ah, Xanthophyll biosynthesis in chromoplasts isolation and molecular cloning of an enzyme catalyzing the conversion of 5,6-epoxycarotenoid into ketocar-otenoid. Plant J. 6, 45, 1994. 

Absorption and Raman analysis of LHCII complexes from xanthophyll biosynthesis mutants and plants containing unusual carotenoids (e.g., lactucoxanthin and lutein-epoxide) should also be interesting, since the role of these pigments and their binding properties are unknown. Understanding the specificity of binding can help to understand the reasons for xanthophyll variety in photosynthetic antennae and aid in the discovery of yet unknown functions for these molecules. 

Prior to 1995, only one locus affecting Xanthophyll biosynthesis in photosynthetic tissues of Arabidopsis had been identified, the ABA i locus, the mutation of which disrupts zeaxanthin deepoxidase, one of two xanthophyll cycle enzymes (Koomneef et al, 1982 Rock and Zeevaart, 1991 Rock et al., 1992). As a step toward advancing understanding of xanthophyll biosynthesis, incorporation, and function in plants, the author s laboratory has screened for and identified mutations defining two additional loci required for xanthophyll biosynthesis in Arabidopsis, LUTl and LUT2 LUT= LUTein deficient). Mutations at either locus result in defects in the synthesis of lutein, the most predominant xanthophyll in plants. Singly and in combination with the aba mutation, these lut mutations have allowed the genetic construction of five distinct mutant lines which differ dramatically in their carotenoid composition relative to wild-type Arabidopsis. In the remainder of this chapter I will first briefly discuss the aba mutation followed by a... 

Stigliani AL, Giorio G, D Ambrosio C (2011) Characterization of P450 carotenoid 6- and e-hydroxylases of tomato and transcriptional regulation of xanthophyll biosynthesis in root, leaf, petal and fruit. Plant Cell Physiol 52 851-865... 

Very few enzymatic studies on xanthophyll biosynthesis in plants have been reported. The conversion of zeaxanthin into antheraxanthin and violaxanthin by lettuce chloroplasts requires molecular oxygen and NAD PH, with pH optima at 7.8 and 7.4 in the light and dark, respectively. The hydroxylation of carotene to )8-cryptoxanthin (3-hydroxy-)3-carotene) also requires NADPH and is probably catalyzed by a mixed-function oxygenase, as the hydroxy group originates from 02- The 5,6-and 5, 6 -epoxy groups are probably formed by a similar mechanism. 

Several hydroxylation reactions in xanthophyll biosynthesis are catalyzed by mixed-function oxidases and are therefore potential target... 

Replacement of the hydrogen at the 3 or 3 position of the carotene ring with a hydroxyl is the next step in both branches of the pathway. Hydroxylation of the rings of the carotenes leads to biosynthesis of the xanthophylls, including the well-known lutein and zeaxanthin food pigments. Lutein is formed by hydroxylation of a-carotene zeaxanthin is formed by hydroxylation of P-carotene. 

Mijts, B.N., Lee, PC., and Schmidt-Dannert, C., Identification of a carotenoid oxygenase synthesizing acyclic xanthophylls combinatorial biosynthesis and directed evolution, Chem. Biol., 12, 453, 2005. 

The variations in the end group structure and conformation are determined by the carotenoid biosynthesis enzymes. These structural features are likely to determine localization as well as functions of these xanthophylls in vivo (Hashimoto et al., 2001 Young et al., 2002). 

Taylor, I. B., T. Sonneveld et al. (2005). Regulation and manipulation of the biosynthesis of abscisic acid, including the supply of xanthophyll precursors. J. Plant Growth Reg. 24(4) 253-273. 

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). 

Carotene is the major dietary precursor of vitamin A and therefore represents a fundamental component in our diet. The later steps of carotenoid biosynthesis in plants involve the formation of xanthophylls, which are oxygenated derivatives. Among these, capsanthin results from the activity of a bifunctional enzyme, the capsanthin-capsorabin synthase (CCS), that catalyses the conversion of the ubiquitous antheraxanthin and violaxanthin, into capsanthin and capsorubin (Fig. 11.3). 

Since increased 02 generation appeared to correlate with increased carotenoid biosynthesis, we examined the effect of DQ exposure on carotenoid levels and composition. Exposure of cultures to DQ increased the levels of carotenoid produced by about 40%, and also increased the relative proportion of xanthophylls and diminished the levels of carotene precursors (31). In addition to producing more carotenoids, the increased proportion of xanthophylls would provide greater resistance to oxidative stress since xanthophylls are generally more effective antioxidants than carotenes (2). This pattern of increased levels of carotenoids and a higher proportion of xanthophylls also takes place as cultures age. The astaxanthin pathway may function in part to prevent aging of yeast and possibly to supply antioxidant capacity to their progeny. Microscopic examination of autofluorescence supported that carotenoids are... 

Pathways. Studies of carotenoid transformations that take place when a mutant strain, PGl, of the green alga Scenedesmus obliquus is transferred from dark to light conditions have indicated that the transformations 15-cw-phytoene (180) 15-c/5-phytofluene (181) - 15-cis- -carotene (182) -> trans-C-caro-tene (183) (Scheme 7) take place in the biosynthesis of the normal cyclic carotenoids. The results were also in agreement with the formation of the xanthophylls lutein (16) and zeaxanthin (174) from the corresponding carotenes. 

Gabellini N, Bowyer JR, Hurt E, Melandri A and Hauska G (1982) A cytochrome b/c complex with ubiquinol-cytochrome C2 oxidoreductase activity from Rhodopseudo-monas sphaeroides. Eur J Biochem 126 105-111 Gilmore AM (1996) Mechanistic aspects of xanthophyll cycle-dependent photoprotection in higher plant chloroplasts and leaves. Physiol Plantarum 98 1-13 Giuliano G, Bartley GE and Scolnik PA (1993) Regulation of carotenoid biosynthesis during tomato development. Plant Cell 5 379-387... 

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