Browsing by Subject "mycosporine-like amino acids"
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(2019)Mycosporines and mycosporine-like amino acids (MAAs) are small-molecules that provide UV protection in a broad range of organisms. Cyanobacteria produce a diverse set of MAA chemical variants, many of which are glycosylated. Even though the biosynthetic pathway for the production of a common cyanobacterial MAA, shinorine, is known, the biosynthetic origins of the glycosylated variants remains unclear. In this work, bioinformatics analyses were performed to catalogue the genetic diversity encoded in the MAA gene clusters in cyanobacterial genomes and identify a set of enzymes that might be involved in MAA biosynthesis. A total of 211 cyanobacterial genomes were found to contain the MAA gene cluster, with six containing glycosyltransferase genes within the gene cluster. Afterwards, 38 strains from the University of Helsinki Culture Collection were tested for the production of MAAs using QTOF-LC/MS analyses. This resulted in the identification of several novel glycosylated MAA chemical variants from Nostoc sp. UHCC 0302, which contained a 7.4 kb MAA biosynthetic gene cluster consisting of 7 genes, including two for glycosyltransferases and one for dioxygenase. Heterologous expression of this gene cluster in Escherichia coli TOP10 resulted in the production of a glycosylated porphyra-334 variant of 509 m/z by the transformant cells, showing that colanic acid biosynthesis glycosyltransferases can catalyse the addition of hexose to MAAs. These results suggested a biosynthetic route for the production of glycosylated MAAs in cyanobacteria and allowed to propose a putative role for dioxygenases in MAA biosynthesis. Further characterization of additional glycosyltransferases is necessary to improve our understanding of glycosylated MAA biosynthesis and functionality, which could be applied to large scale processes and be used in industrial applications.
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(2023)Continuous exposure to ultraviolet radiation can cause detrimental health effects in humans, including erythema, hyperpigmentation, photo-aging, and skin cancer. Sunscreens provide important protection of skin against the harmful effects of ultraviolet radiation. However, chemical and physical sunblock filters can be harmful for both human beings and the environment. There is a need for natural alternatives to commercial filters currently used in sunscreens. Mycosporine-like amino acids (MAAs) are natural microbial sunscreens produced mainly by marine organisms to protect themselves from ultraviolet radiation. There has been over three decades of interest in these natural compounds for applications in the cosmetic industry. However, low production levels in nature have hindered large-scale processes for industrial applications. Here, we demonstrates the successful expression of a MAA biosynthetic pathway from cyanobacteria in a metabolically engineered strain of Escherichia coli. Heterologous expression of the artificial codon-optimized MAA biosynthetic pathway resulted in high-level production of porphyra-334 and shinorine. These two MAAs have exceptional high molar extinction coefficients and are found in a number of commercial sunscreen formulations that rely on algal extracts. The expression of a gene encoding an ABC-transporter, which is associated with cryptic MAA biosynthetic gene clusters in cyanobacteria, in Escherichia coli resulted in the effective transport of both porphyra-334 and shinorine outside the cell. Together, these two advances improve the possibility of biotechnological production of these microbial sunscreens in industrial microbial hosts.
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