violaxanthin and fucoxanthin

Fucoxanthin and its derivatives are the main light-harvesting pigments in the photosynthetic apparatus of many chromalveolate algae and represent the most abundant carotenoids in the world's oceans, thus being major facilitators of marine primary production. A central step in fucoxanthin biosynthesis that has been elusive so far is the conversion of violaxanthin to neoxanthin. Here, we show that in chromalveolates, this reaction is catalyzed by violaxanthin de-epoxidase-like (VDL) proteins and that VDL is also involved in the formation of other light-harvesting carotenoids such as peridinin or vaucheriaxanthin. VDL is closely related to the photoprotective enzyme violaxanthin de-epoxidase that operates in plants and most algae, revealing that in major phyla of marine algae, an ancient gene duplication triggered the evolution of carotenoid functions beyond photoprotection toward light harvesting.

Topics: Algal Proteins; Aquatic Organisms; Carotenoids; Chlorophyll A; Gene Expression Regulation; Light-Harvesting Protein Complexes; Oxidoreductases; Phaeophyceae; Phylogeny; Xanthophylls

The influence of six different light regimes throughout the photosynthetically active radiation range (from 400 to 700 nm, including blue, green, yellow, red-orange, red, and white) at two intensities (100 and 300 µmol photons m

Topics: beta Carotene; Chlorophyll; Diatoms; Light; Photosynthesis; Pigments, Biological; Xanthophylls; Zeaxanthins

LC with photodiode array and APCI-ion trap mass spectrometry has made it possible to tentatively identify 76 carotenyl fatty acid esters (cFAEs) in solvent extracts from Dreissena bugensis, collected from Lake Erie: 16 mono- and 33 diFAEs of fucoxanthinol (FOH), and 27 diFAEs of mactraxanthin (MX). FOH and MX, previously identified in cFAE hydrolysates, were confirmed as parent carotenoids of the cFAEs, and as primary metabolites of fucoxanthin and violaxanthin, respectively, derived from diatoms and chlorophytes in the dreissenids' diet. The most abundant fatty acid substituents of cFAEs were 16:0 and 16:1; abundant fatty acid biomarkers were 16:1 and 20:5, from diatoms, and 17:0, from bacteria. Cleanup of solvent extracts by solid phase extraction (Florisil) was necessary to reduce neutral background lipids, which interfered with detection of MX-diFAEs by APCI(+), and detection of FOH-diFAEs by APCI(+/-). The FOH-monoFAEs, MX-diFAEs and FOH-diFAEs were found to elute in a well-defined chromatographic order, by two regression models for retention times increasing as a function of: i) increasing number of carbons but decreasing number of double bonds in the fatty acid and decreasing number of non-esterified OH-groups on the parent carotenoids; ii) increasing dispersive but decreasing polar and hydrogen-bonding interactions, described by solubility parameters calculated for each cFAE. The best separations of the dreissenid cFAEs, with free OH-groups decreasing from four to one, were achieved between 20 and 68min, using a C18-column and moderately polar mobile phase (acetone, water), to obtain a reverse-phase gradient with a 56% decrease in hydrogen-bonding interactions.

Topics: Animals; beta Carotene; Carotenoids; Chromatography, Liquid; Dreissena; Esters; Fatty Acids; Fresh Water; Mass Spectrometry; Solid Phase Extraction; Xanthophylls

The biosynthesis pathway to diadinoxanthin and fucoxanthin was elucidated in Phaeodactylum tricornutum by a combined approach involving metabolite analysis identification of gene function. For the initial steps leading to β-carotene, putative genes were selected from the genomic database and the function of several of them identified by genetic pathway complementation in Escherichia coli. They included genes encoding a phytoene synthase, a phytoene desaturase, a ζ-carotene desaturase, and a lycopene β-cyclase. Intermediates of the pathway beyond β-carotene, present in trace amounts, were separated by TLC and identified as violaxanthin and neoxanthin in the enriched fraction. Neoxanthin is a branching point for the synthesis of both diadinoxanthin and fucoxanthin and the mechanisms for their formation were proposed. A single isomerization of one of the allenic double bounds in neoxanthin yields diadinoxanhin. Two reactions, hydroxylation at C8 in combination with a keto-enol tautomerization and acetylation of the 3'-HO group results in the formation of fucoxanthin.

Topics: beta Carotene; Biosynthetic Pathways; Carotenoids; Diatoms; Escherichia coli; Genetic Complementation Test; Geranylgeranyl-Diphosphate Geranylgeranyltransferase; Intramolecular Lyases; Oxidoreductases; Phylogeny; Xanthophylls; zeta Carotene

Recently, we reported the presence of the violaxanthin-antheraxanthin-zeaxanthin cycle in diatoms, and showed that violaxanthin is the putative precursor of both diadinoxanthin and fucoxanthin in the diatom Phaeodactylum tricornutum Bohlin (M. Lohr and C. Wilhelm, 1999, Proc. Natl. Acad. Sci. USA 96: 8784-8789). In the present study, two possible intermediates in the synthesis of violaxanthin from beta-carotene were identified in P. tricornutum, namely beta-cryptoxanthin and beta-cryptoxanthin epoxide. In low light, the latter pigment prevails, but in high light beta-cryptoxanthin accumulates, probably as the result of an increased activity of the xantophyll-cycle de-epoxidase. The apparent kinetics of several xanthophyll conversion steps were determined for P. tricornutum and Cyclotella meneghiniana Kuitzing. The experimentally determined conversion rates were used to evaluate the hypothetical pathway of xanthophyll synthesis in diatoms. For this purpose a mathematical model was developed which allows the calculation of theoretical rates of pigment conversion for microalgae under steady-state growth conditions. A comparison between measured and calculated conversion rates agreed well with the proposal of a sequential synthesis of fucoxanthin via violaxanthin and diadinoxanthin. The postulation of zeaxanthin as an obligatory intermediate in the synthesis of violaxanthin, however, resulted in large discrepancies between the measured and calculated rates of its epoxidation. Instead of zeaxanthin, beta-cryptoxanthin epoxide may be involved in the biosynthesis of violaxanthin in diatoms.

Topics: Antioxidants; beta Carotene; Carotenoids; Chromatography, High Pressure Liquid; Cryptoxanthins; Diatoms; Dithioerythritol; Epoxy Compounds; Herbicides; Light; Lutein; Models, Biological; Pigments, Biological; Pyridazines; Sulfhydryl Reagents; Xanthophylls; Zeaxanthins

According to general agreement, all photosynthetic organisms using xanthophyll cycling for photoprotection contain either the violaxanthin (Vx) cycle or the diadinoxanthin (Ddx) cycle instead. Here, we report the temporal accumulation of substantial amounts of pigments of the Vx cycle under prolonged high-light stress in several microalgae thought to possess only the Ddx cycle. In the diatom Phaeodactylum tricornutum, used as a model organism, these pigments also participate in xanthophyll cycling, and their accumulation depends on de novo synthesis of carotenoids and on deepoxidase activity. Furthermore, our data strongly suggest a biosynthetic sequence from Vx via Ddx to fucoxanthin in P. tricornutum. This gives experimental support to the long-stated hypothesis that Vx is a common precursor of all carotenoids with an allenic or acetylenic group, including the main light-harvesting carotenoids in most chlorophyll a/c-containing algae. Thus, another important function for xanthophyll cycling may be to optimize the biosynthesis of light-harvesting xanthophylls under fluctuating light conditions.

Topics: beta Carotene; Carotenoids; Cells, Cultured; Chromatography, High Pressure Liquid; Diatoms; Dithiothreitol; Enzyme Inhibitors; Epoxy Compounds; Eukaryota; Kinetics; Light; Lutein; Molecular Structure; Pigments, Biological; Xanthophylls

The pigment composition of the light-harvesting complexes isolated from several brown algae belonging to different orders has been analysed by reverse-phase HPLC. Relative to whole chloroplasts, they were markedly enriched in Chl c, fucoxanthin and violaxanthin and conversely depleted in Chl a. The relative molar proportions of the 4 main pigments (Chl a/Chl c/fucoxanthin/violaxanthin) ranged from 100:18:76:6 to 100:30:107:17. The protein moiety of LH complexes of all the species studied were composed of one or two main polypeptide components in the range of 19-22 kDa. These polypeptide subunits were arranged in polymeric particles about 240 kDa in Laminaria saccharina. A polyclonal antibody raised against the LH polypeptide of Fucus serratus has been tested on LH apoproteins of other Chromophytes and Chlorophytes. Phylogenic implications of these results are discussed.

Topics: Amino Acids; Antibodies, Fungal; beta Carotene; Carotenoids; Chloroplasts; Cross Reactions; Phaeophyceae; Pigments, Biological; Spectrometry, Fluorescence; Ultracentrifugation; Xanthophylls

Acrocarpia paniculata thylakoids were fragmented with Triton X-100 and the pigment-protein complexes so released were isolated by sucrose density gradient centrifugation. Three main chlorophyll-carotenoid-protein complexes with distinct pigment compositions were isolated. (1) A P-700-chlorophyll a-protein complex, with a ratio of 1 P-700: 38 chlorophyll a: 4 beta-carotene molecules, had similar absorption and fluorescence characteristics to the chlorophyll-protein complex 1 isolated with Triton X-100 from higher plants, green algae and Ecklonia radiata. (2) an orange-brown complex had a chlorophyll a : c2 : fucoxanthin molar ratio of 2 : 1 : 2. this complex had no chlorophyll c1 and contained most of the fucoxanthin present in the chloroplasts. This pigment complex is postulated to be the main light-harvesting complex of brown seaweeds. (3) A green complex had a chlorophyll a : c1 : c2 : violaxanthin molar ratio of 8 : 1 : 1. This also is a light-harvesting complex. the absorption and fluorescence spectral characteristics and other physical properties were consistent with the pigments of these three major complexes being bound to protein. Differential extraction of brown algal thylakoids with Triton X-100 showed that a chlorophyll c2-fucoxanthin-protein complex was a minor pigment complex of these thylakoids.

Topics: beta Carotene; Carotenoids; Centrifugation, Density Gradient; Chlorophyll; Chloroplasts; Phaeophyceae; Photochemistry; Pigments, Biological; Plant Proteins; Seaweed; Spectrometry, Fluorescence; Spectrum Analysis; Xanthophylls