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Mycosporine-glycine

As well as functioning as natural UV-protective compounds, some MAAs such as mycosporine-glycine also have moderate antioxidant activity (Dunlap and Yamamoto 1995). In addition, the presumed biochemical precursor of MAAs, 4-deoxygadusol exhibits strong antioxidant activity (Dunlap et al. 1998). The photo-physicochemical properties of MAAs guarantee both a high UV-protective effectiveness in combination with antioxidant capabilities. [Pg.287]

Dunlap, W. C. and Yamamoto, Y., Small-molecule antioxidants in marine organisms antioxidant activity of mycosporine-glycine, Comp. Biochem. Physiol., 112B, 105, 1995. [Pg.29]

Cells have substantial chemical defenses against the UV photoproducts produced in seawater and intracellular fluids. Many organisms have antioxidants (e.g., carotenoids, ascorbate, tocopherols, anthocyanins, and tridentatols) that quench photo-oxidative reactions.64-67 Cells also have enzymes (e.g., catalase and superoxide dismutase) that can counteract the oxidative nature of peroxides and other radicals.26 Some compounds, such as the UV-absorbing pigment melanin, can act as both optical filter and antioxidant.68 The MAA mycosporine-glycine (Figure 15.3) functions in a similar dual capacity.69 The role of UV-mediated reactions in seawater relative to biological effects is an important current area of study. [Pg.486]

Mycosporine-glycine valine MV c15h24n2o7 344 335 Euphausia superba107... [Pg.489]

Several surveys have been undertaken to evaluate possible habitat or behavioral patterns in MAA distribution and content, but only a few general trends in MAA occurrence are evident.107-110-112117 Analyses of 382 species reveal that 95% of tropical species, 80% of temperate species and 82% of polar species have detectable levels of MAAs (Table 15.3). Palythine, shinorine, porphyra-334, mycosporine-glycine, asterina-330, palythinol, palythene, and mycosporine-2-glycine have been found at all latitudes. Other MAAs are less frequently reported and have more limited distributions however, this may be a function of insufficient data and not a true representation of MAA occurrence. [Pg.493]

An MAA with a possible restricted geographic occurrence is mycosporine-glycine valine. This MAA was first described from a survey of Antarctic species and was initially observed only in consumer organisms (invertebrates and fish), not any of the sampled primary producers.107 Subsequent studies in the Antarctic have identified this MAA in the diatom Fragilariopsis cylindrus, the haptophyte Phaeocystis sp., and mixed assemblages of Southern Ocean phytoplankton.124 126 128 There have been a few tentative identifications of mycosporine-glycine valine in organisms from... [Pg.497]

Observed changes in palythene and palythinol, not mycosporine-glycine. [Pg.503]

Various MAA compounds have different responses to partitioned radiation exposures. In whole water samples of Antarctic phytoplankton monitored over a 2-week period, shinorine and porphyra-334 increased in concentration with exposure to either total sunlight or visible light alone.173 In contrast, mycosporine-glycine and palythine concentrations increased only under total sunlight treatments and not when exposure was limited to the visible band. MAA-specific increases also occur in unicellular freshwater Chlorophyta species.131... [Pg.504]

Extracellular occurrence of MAAs is common in corals where these UV-absorbing compounds are found in the external mucus layer of the colony.163 176 MAA concentrations in mucus layers are closely matched to or occasionally less than the MAA concentrations in the coral tissues, indicating that MAAs are probably passively and nonselectively excreted.176 Consideration of the MAA content and optical path length of the mucus layer ( 1 mm) gives an estimated absorbance efficiency of approximately 7% of incident UV. Such low attenuation of UV radiation probably does not provide substantial protection for the living polyps, and it may be the antioxidant properties of mycosporine-glycine that are more important in the mucus layer (see also Section II.A.10). [Pg.505]


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See also in sourсe #XX -- [ Pg.492 ]




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