Carotenoid Metabolism in Plants
Therefore, fucoxanthin may have the potential toreduce the risk of cancer induced by reactive nitrogen species.
Neoxanthin is another common alleniccarotenoid, widely distributed in higher plants and algae, which was firstisolated from the green leaves of barley in 1938 by Strain HH.
, 6 x Vitamin synthesis in plants ..
Carotenoids are widely distributed pigments in nature and their biosynthetic pathway has been extensively studied in various organisms. The recent access to the overwhelming amount genomic data of cyanobacteria has given birth to a novel approach called comparative genomics. The putative enzymes involved in the carotenoid biosynthesis among the cyanobacteria were determined by similarity-based tools. The reconstruction of biosynthetic pathway was based on the related enzymes. It is interesting to find that nearly all the cyanobacteria share quite similar pathway to synthesize β-carotene except for PCC 7421. The enzymes, crtE-B-P-Qb-L, involved in the upstream pathway are more conserved than the subsequent ones (crtW-R). In addition, many carotenoid synthesis enzymes exhibit diversity in structure and function. Such examples in the families of ζ –carotene desaturase, lycopene cylases and carotene ketolases were described in this article. When we mapped these genes to the cyanobacterial genomes, the genes showed great structural variation among species. All of them are dispersed on the whole chromosome in contrast to the linear adjacent distribution of the gene cluster in other eubacteria. Moreover, in unicellular cyanobacteria, each step of the carotenogenic pathway is usually catalyzed by one gene product, whereas multiple ketolase genes are found in filamentous cyanobacteria. Such increased numbers of genes and their correlation to the ecological adaptation were carefully discussed.
Among these compounds, echinenone and canthaxantin are abundant in cyanobacteria are characteristic of cyanobacteria ().
Violaxanthin is an epoxidized derivative of antheraxanthin (hydroxylated cryptoxanthin) and forms with zeaxanthin the xanthophyll cycle that is said to protect the photosynthetic system of plants against damage by excess light.
Concentration of photosynthetic pigments and …
8. Armstrong GA, Alberti M, Hearst JE. Conserved enzymes mediate the early reactions of carotenoid biosynthesis in nonphotosynthetic and photosynthetic prokaryotes. 1990;87:9975- 9979
hydrocarbons: alkanes, alkenes, carotenoids - Lipid
10. Phadwal K. Carotenoid biosynthetic pathway: molecular phylogenies and evolutionary behavior of crt genes in eubacteria. 2005;345:35- 43
Rosal Medicinal Plants - StuartXchange
Each of these enzymes is a single-gene produce in most cases. Multiple copies of ketolases were only identified in the filamentous species. Actually, two carotenoid ketolase genes crtW38 and crtW148 were cloned from the cyanobacterium, PCC 73102 and functionally characterized . Scanning the genomics of all species for genes by the similarity search we also found two crtO ketolases and two crtW existed in PCC 73102 and ATCC 29413 respectively. There are no paralogous copies of genes other than in filamentous cyanobacteria. Most of filamentous cyanobacteria exhibit a wide range of ecological tolerance and are found in freshwater, marine and terrestrial habitats. The increased number of isozymes associated with pigment biosynthesis in filamentous cyanobacteria relative to unicellular species may be related to increased regulatory demands and perhaps also to different local environments.
Phytohormones and their metabolic engineering for …
13. Linden H, Misawa N, Saito T, Sandmann G. A novel carotenoid biosynthesis gene coding for ζ-carotene desaturase: functional expression, sequence and phylogenetic origin. 1994;24:369-379
Light Quality in Plant Growth and Development
14. Breitenbach J, Fernández-González B, Vioque A, Sandmann G. A higher-plant type ζ-carotene desaturase in the cyanobacterium PCC 6803. 1998;36:725-732