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Scytonemin is a pigment synthesized by cyanobacteria and found in their sheath. The importance of this biomolecule is its photoprotective function, which is one of the major survival strategies adopted by extremophiles under stressed conditions. Scytonemin has been identified as a prime biomarker in the search for past or present life on planetary...
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... Scytonemin may also interact with other extracellular components in the matrix, such as WspA protein, to indirectly function in the desiccation resistance [38]. Scytonemin and iron can form the iron-complexes that possibly facilitate the survival of cyanobacterial colonies on sandstone rocks [51,52]. ...
Scytonemin is a promising UV-screen and antioxidant small molecule with commercial value in cosmetics and medicine. It is solely biosynthesized in some cyanobacteria. Recently, its biosynthesis mechanism has been elucidated in the model cyanobacterium Nostoc punctiforme PCC 73102. The direct precursors for scytonemin biosynthesis are tryptophan and p-hydroxyphenylpyruvate, which are generated through the shikimate and aromatic amino acid biosynthesis pathway. More upstream substrates are the central carbon metabolism intermediates phosphoenolpyruvate and erythrose-4-phosphate. Thus, it is a long route to synthesize scytonemin from the fixed atmospheric CO2 in cyanobacteria. Metabolic engineering has risen as an important biotechnological means for achieving sustainable high-efficiency and high-yield target metabolites. In this review, we summarized the biochemical properties of this molecule, its biosynthetic gene clusters and transcriptional regulations, the associated carbon flux-driving progresses, and the host selection and biosynthetic strategies, with the aim to expand our understanding on engineering suitable cyanobacteria for cost-effective production of scytonemin in future practices.
... The selection of the method should consider the end purpose of the sample. Relatively new techniques implemented on scytonemin characterization, like Raman spectroscopy, are purposed for the identification of scytonemin derived novel compounds (Varnali and Edwards, 2013;Varnali and Gören, 2018). The use of coherent anti-Stokes Raman scattering (CARS) microscopy made possible the reliable identification of scytonemin on live cultures (Venckus et al., 2018). ...
Ultraviolet radiation (UVR) has detrimental effects on human health. It induces oxidative stress, deregulates signaling mechanisms, and produces DNA mutations, factors that ultimately can lead to the development of skin cancer. Therefore, reducing exposure to UVR is of major importance. Among available measures to diminish exposure is the use of sunscreens. However, recent studies indicate that several of the currently used filters have adverse effects on marine ecosystems and human health. This situation leads to the search for new photoprotective compounds that, apart from offering protection, are environmentally friendly. The answer may lie in the same marine ecosystems since molecules such as mycosporine-like amino acids (MAAs) and scytonemin can serve as the defense system of some marine organisms against UVR. This review will discuss the harmful effects of UVR and the mechanisms that microalgae have developed to cope with it. Then it will focus on the biological distribution, characteristics, extraction, and purification methods of MAAs and scytonemin molecules to finally assess its potential as new filters for sunscreen formulation.
... Biosynthesis of sun-screening compounds such as scytonemin is an important strategy for counteracting with harmful UV radiation as it has capacity of shielding cells from the damaging hitting photons [6]. New findings have revealed important information related to structure, genetics, biosynthesis and potential application of scytonemin as sunscreen [29][30][31][32] Scytonemin is extraordinary cyanobacterial secondary metabolite having remarkable stability, possess extraordinary photo-protection and have unique chemical [14,[33][34]. In silico molecular docking studies of dimethoxyscytonemin with human PLK-1 was performed for accessing anticancerous property of this form of scytonemin targeting PLK-1. ...
Cancer is one of the major causes of death throughout the globe. It is expected that the number of new reports with cancer cases will reach twenty two million in the coming two decades. Africa, Central and South America and Asia will have more than 60 percent of the world's new cancer reports and 70 percent of the world's deaths from cancer will be contributed by these continents. Hence, drug discovery for treatment of cancer is the most worked area of this century. Polo-like kinase 1 (PLK-1) is highly expressed in human tumors and is important target of anti-cancerous drugs owing to its role in cell cycle events. It is crucial in maintenance of stability of genome and during different stages of mitosis. Scytonemin is a lipid-soluble and yellow-brown pigment exclusively synthesized by several cyanobacterial species in response to ultraviolet-A radiation. It functions as a photoprotective compound and can act as non-competitive and competitive inhibitor of PLK-1. Other kinases such as Myt1, cyclin-dependent kinase 1/cyclin B, checkpoint kinase 1 and protein kinase C are also inhibited by scytonemin. In the present study, molecular docking approach has been employed for positioning the inhibitor (dimethoxyscytonemin) into the active site of PLK-1 for determining the most probable binding mode. Based on the docking studies, the models which are developed could be utilized for understanding the structure-activity relationships of the scytonemins and for the prescreening and designing of novel inhibitors of PLK-1.
... A theoretical study on iron-scytonemin complexes was reported by Varnali and Gören [113]. Two new model structures in which two scytonemin molecules form sandwich complexes with iron(III) were proposed, and their predicted Raman spectra were compared with that of the parent scytonemin. ...
The contents of issues 5 and 6 of Structural Chemistry from the calendar year 2018 are summarized in the present review. A brief thermochemical commentary and recommendations for future research have been added to the summary of each paper.
... Qualitative identification of different forms of scytonemins can be achieved by Raman spectroscopy, which is based on fundamental vibration modes that can be assigned to specific chemical functional groups. Recently, using Raman spectroscopy, a novel structure of scytonemin has been identified where two scytonemin molecules interact with iron (III) to form sandwich complexes [67]. Thus, Raman spectroscopy can be a useful technique for solving the structure of scytonemin molecules forming a complex with other ions. ...
Scytonemin is a lipid-soluble, highly stable, yellow–brown-coloured secondary metabolite that is accumulated in the extracellular polysaccharide sheath of several but not all members of cyanobacteria. Chemically, scytonemin is an indole alkaloid composed of two heterocyclic units symmetrically connected through a carbon–carbon bond. Thus, scytonemin is unique among natural products due to its special structure, location in a cell, as well as strong absorption maxima in UV-A in addition to the violet–blue region. Traditionally, scytonemin is a well-established photoprotective compound against ultraviolet radiation. Its accumulation in the cyanobacterial sheath has been suggested to be a strategy adopted by several cyanobacteria to protect their cellular components against damaging effects of UVR. Additionally, recent studies have also established the importance of scytonemin in reactive oxygen species scavenging as well as in controlling the growth of cancerous cells. Thus, scytonemin is both ecologically as well as pharmaceutically important metabolite. Recent developments made in the biochemistry and genetics of this compound have paved the way for its application and commercialization for human welfare. This review aims to present a brief history of the compound with chronological developments made in the study of scytonemin and emphasizes its physiochemistry, analytical chemistry, biochemistry, and genetics. We provide a separate section for metabolic engineering and potential applications of scytonemin, mainly as sunscreen and anti-cancerous drugs. We also discuss the future research directions which need to be worked out.
Consumers' growing concern regarding sustainability and environment-friendly products has made the algal- and cyanobacterial-based metabolites an attractive alternative. Scytonemin is one such secondary metabolite, exploited mainly for its photoprotective function and found exclusively in many cyanobacterial species from diverse habitats. In natural settings, the complex interplay of various stress factors affects its synthesis. The genetic and biochemical pathways of the synthesis of this compound are well established, making further genetic modifications, synthetic biology approaches, and bioinformatics analyses easier. However, the role of various stress factors is comparatively less studied. This review presents a concise account of scytonemin: the progress made so far, and the areas never explored to date, briefly including the much-discussed genetic aspects. Compared to other bioinspired secondary metabolites with a wide range of applications, the research in areas related to scytonemin has been slower, despite its early discovery. The discovery of multiple beneficial effects of this compound from various mechanistic studies and the trend of sustainability among consumers can help scytonemin hold a central place in the cosmetic industry as an alternative organic sunscreen agent.
Raman spectroscopy allows the detection and discrimination between microbial pigments of different origins, including carotenoids, chlorophylls and less commonly found violet and brown non-photosynthetic pigments. This review reports examples of Raman spectroscopic studies on violet and brown pigments produced by microorganisms. Examples of investigations on the biological pigments scytonemin, gloeocapsin, violacein, phycocyanin, and prodigiosin are reviewed. Raman spectroscopy is a fast, simple and direct analytical tool which has been appreciated by microbiologists and chemists but more recently also by those who study natural geobiological processes in real-world systems. Different Raman spectroscopic approaches including confocal Raman spectrometry, FT-Raman spectroscopic possibilities, and SERS modes are reviewed for possibilities of following distribution of pigments at the cellular level in microbial cultures or in native endoliths, including confocal Raman spectrometry, FT-Raman spectroscopic possibilities, and SERS modes. New fast Raman mapping techniques are increasingly used, as well as portable systems. Special possibilities of high relevance for geoscience, geobiology or applied microbiology are opened up by the recent revolutionary technical developments, including the availability of portable and handheld tools that can be used directly on rocky outcrops to study native microbial colonization in situ.
