Mycosporine-like amino acid

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Mycosporine-like amino acids (MAAs) are small

secondary metabolites produced by organisms that live in environments with high volumes of sunlight, usually marine environments. The exact number of compounds within this class of natural products is yet to be determined, since they have only relatively recently been discovered and novel molecular species are constantly being discovered; however, to date their number is around 30.[1][2] They are commonly described as “microbial sunscreens” although their function is believed not to be limited to sun protection.[3] MAAs represent high potential in cosmetics, and biotechnological applications. Indeed, their UV-absorbing properties would allow to create products derived from natural photoprotectors, potentially harmless to the environment and efficient against UV damage.[4]

Background

MAAs are widespread in the microbial world and have been reported in many microorganisms including

heat stress.[12]

Chemistry

Mycosporine–like amino acids are rather small molecules (<400

primary metabolism.[16] An example is the shikimate pathway that is classically used to produce the aromatic amino acids (phenylalanine, tyrosine and tryptophan); with many intermediates and enzymes from this pathway utilized in MAA biosynthesis.[16]

Examples

name peak absorbance nm systematic name Chemspider
Asterina-330 330 {[(3E)-5-Hydroxy-3-[(2-hydroxyethyl)iminio]-5-(hydroxymethyl)-2-methoxy-1-cyclohexen-1-yl]amino}acetate 10475832
Euhalothece-362 362
Mycosporine-2-glycine 334 [(E)-{3-[(Carboxymethyl)amino]-5-hydroxy-5-(hydroxymethyl)-2-methoxy-2-cyclohexen-1-ylidene}amino]acetic acid 10474079
Mycosporine-glycine 310 N-[(5S)-5-Hydroxy-5-(hydroxymethyl)-2-methoxy-3-oxo-1-cyclohexen-1-yl]glycine 10476943
Mycosporine-glycine-valine 335
Mycosporine-glutamic acid-glycine 330
Mycosporine-methylamine-serine 327
Mycosporine-methylamine-threonine 327
Mycosporine-taurine 309
Palythenic acid 337
Palythene 360 [(E)-{5-Hydroxy-5-(hydroxymethyl)-2-methoxy-3-[(1E)-1-propen-1-ylamino]-2-cyclohexen-1-ylidene}ammonio]acetate 10475813
Palythine 320 N-[5-Hydroxy-5-(hydroxymethyl)-3-imino-2-methoxycyclohex-1-en-1-yl]glycine 10272813
Palythine-serine 320 N-[5-Hydroxy-5-(hydroxymethyl)-3-imino-2-methoxy-1-cyclohexen-1-yl]serine 10476937
Palythine-serine-sulfate 320
Palythinol 332
Porphyra-334 334 29390215
Shinorine 334
Usujirene 357

[17]

Functions

Ultraviolet light responses

Protection from UV radiation

Ultraviolet

diatoms.[3] MAAs have also been identified in 572 species of other algae : 45 species in Chlorophyta, 41 species in Phaeophyta, 486 species in Rhodophyta [21] which also present anti-aging, anti-inflammatory, antioxidative and wound healing properties. When MAAs absorb UV light the energy is dissipated as heat.[22][23] UV-B photoreceptors have been identified in cyanobacteria as the molecules responsible for the UV light induced responses, including synthesis of MAAs.[24] Helioguard™365 containing Porphyra-334 and shinorine derived from Porphyra umbilicalis is already a creme on the market were developed by Mibelle AG biochemistry and shows preventive effects against UVA. An MAA known as palythine, derived from seaweed, has been found to protect human skin cells from UV radiation even in low concentrations.[25]

"MAAs, in addition to their environmental benefits, appear to be multifunctional photoprotective compounds," says Dr. Karl Lawrence, lead author of a paper on the research. "They work through the direct absorption of UVR [ultraviolet radiation] photons, much like the synthetic filters. They also act as potent antioxidants, which is an important property as exposure to solar radiation induces high levels of oxidative stress, and this is something not seen in synthetic filters."

Protection from oxidative damage

Some MAAs protect cells from reactive oxygen species (i.e.

hydroxyl radicals very quickly and efficiently.[28] Some oceanic microbial ecosystems are exposed to high concentrations of oxygen and intense light; these conditions are likely to generate high levels of reactive oxygen species. In these ecosystems, MAA-rich cyanobacteria may be providing antioxidant activity.[29]

Accessory pigments in photosynthesis

MAAs are able to absorb

UV light. A study published in 1976 demonstrated that an increase in MAA content was associated with an increase in photosynthetic respiration.[30] Further studies done in marine cyanobacteria showed that the MAAs synthesized in response to UV-B correlated with an increase in photosynthetic pigments.[31] Though not absolute proof, these findings do implicate MAAs as accessory pigments to photosynthesis
.

Photoreceptors

The eyes for the mantis shrimp contain four different kinds of mycosporine-like amino acids as filters, which combined with two different visual pigments assist the eye to detect six different bands of ultraviolet light.[32] Three of the filter MAAs are identified with porphyra-334, mycosporine-gly, and gadusol.[33]

Environmental stress responses

Salt stress

Osmotic stress is defined as difficulty maintaining proper fluids in the cell within a

solutes
must be present as well.

Desiccation stress

UV radiation and oxidation stress have been shown to possess MAA’s in an extracellular matrix.[36] However it has been shown that MAAs do not provide sufficient protection against high doses of UV radiation.[6]

Thermal stress

Thermal (heat) stress is defined as temperatures lethal or inhibitory towards growth. MAA concentrations have been shown to be up-regulated when an organism is under thermal stress.[37][38] Multipurpose MAAs could also be compatible solutes under freezing conditions, because a high incidence of MAA producing organisms have been reported in cold aquatic environments.[3]

References

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  7. ^ Okaichi T, Tokumura T. Isolation of cyclohexene derivatives from Noctiluca miliaris. 1980 Chemical Society of Japan
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  32. ^ "With 'biological sunscreen,' mantis shrimp see the reef in a whole different light". 3 July 2014. Retrieved 4 July 2014.
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Further reading

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