Heterologous Production of Cyanobacterial Mycosporine-Like Amino Acids Mycosporine-Ornithine and Mycosporine-Lysine in Escherichia coli

Abstract

Mycosporine-like amino acids (MAAs) are an important class of secondary metabolites known for their protection against UV radiation and other stress factors. Cyanobacteria produce a variety of MAAs, including shinorine, the active ingredient in many sunscreen creams. Bioinformatic analysis of the genome of the soil-dwelling cyanobacterium Cylindrospermum stagnale PCC 7417 revealed a new gene cluster with homology to MAA synthase from Nostoc punctiforme. This newly identified gene cluster is unusual because it has five biosynthesis genes (mylA to mylE), compared to the four found in other MAA gene clusters. Heterologous expression of mylA to mylE in Escherichia coli resulted in the production of mycosporine-lysine and the novel compound mycosporine-ornithine. To our knowledge, this is the first time these compounds have been heterologously produced in E. coli and structurally characterized via direct spectral guidance. This study offers insight into the diversity, biosynthesis, and structure of cyanobacterial MAAs and highlights their amenability to heterologous production methods. M ycosporine-like amino acids (MAAs) are commonly found in marine microbes exposed to high levels of UV radiation, including aquatic fungi, eukaryotic algae, and cyanobacteria (1-6). These small (Ͻ400 Da), colorless, water-soluble compounds are composed of a 4-deoxygadusol core conjugated with an amino acid or alcohol (7). Their absorption maxima typically range from 310 to 360 nm and their molar extinction coefficients (ε) range from 28,100 to 50,000 M Ϫ1 cm Ϫ1 (8, 9). Commonly termed "microbial sunscreens," MAAs can dissipate UV energy as heat without generating free oxygen radicals (7).While UV exposure is necessary to elicit the synthesis of MAAs (10), some studies suggest that other factors, including osmotic stress, may also be involved in MAA regulation (11). Indeed, MAAs are widely considered to be multifunctional compounds offering protection against oxidative, osmotic, and thermal stress as well as UV radiation (12-17). However, this may not be true for all MAAs (11). Due to their diverse biological properties, MAAs are promising candidates for pharmaceutical and cosmetic applications (3, 18). For example, shinorine, produced by the cyanobacterium Anabaena variabilis, has already been commercialized as an active ingredient in sunscreen creams (Helioguard 365 and Helionori) (14).The biosynthesis of shinorine ( Fig. 1) was recently elucidated via heterologous expression in Escherichia coli (19,20) and is a model pathway for MAA biosynthesis. In A. variabilis ATCC 29413, the shinorine biosynthesis gene cluster consists of four genes: ava_3855 to ava_3858. The first step in the biosynthesis of shinorine is the conversion of sedoheptulose-7-phosphate (SH-7P) to 2-demethyl-4-deoxygadusol (DDG) by a DDG synthase (Ava_3858). Following this, DDG is converted to the mycosporine core compound 4-deoxygadusol (4-DG) by an O-methyltransferase (O-MT) (Ava_3857). Glycylation of 4-DG is catalyzed by a C-N ligase (Ava_3856), resulting ...

Characterization of mycosporine-like amino acids in the cyanobacterium <i>Nostoc verrucosum</i>

“…The mysABCD genes often form a gene cluster and are distributed in a variety of cyanobacterial species (Gao and Garcia-Pichel, 2011;Hu et al, 2015). In general, the presence of the mys genes is thought to relate to the MAAproducing capability in microorganisms (Katoch et al, 2016;Miyamoto et al, 2014). There are the mysABC gene cluster and the mysD gene in N. verrucosum strain KU005, consistent with the presence of porphyra-334 and shinorine (Fig.…”

Four chemotypes of the terrestrial cyanobacterium Nostoc commune characterized by differences in the mycosporine‐like amino acids

“…; Katoch et al . ). These cyanobacterial species are thought to have shinorine and/or porphyra‐334 synthesizing capacity.…”

Cyanobacteria as efficient producers of mycosporine‐like amino acids

“…Analogs of MAAs like tetrahydopyridine products have been used commercially as sunscreen agents . Furthermore, two commercial products (Helioguard ® and Helionori ® ) containing MAAs extract from red alga Porphyra umbilicalis are already in market . Apart from UV protectants, MAAs have been utilized as photostabilizing additives in plastics, paints and varnishes .…”