Abstract
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.
Highlights
Cyanobacteria are photoautotrophic prokaryotes that can directly convert CO2 into organic compounds using solar energy
To cope with the extreme and changeable environments, cyanobacteria have developed a wide range of adaptive mechanisms
Some cyanobacteria are directly exposed to strong sunlight in native habitats, such as those dwelling in intertidal mats or on desert soil surfaces [6,7,8]
Summary
Cyanobacteria are photoautotrophic prokaryotes that can directly convert CO2 into organic compounds using solar energy. To eliminate the deleterious effects of UV radiation, one of the most important strategies in some cyanobacteria is to generate UV-absorbing compounds, such as mycosporine-like amino acids (MAAs) and scytonemin [10]. Both compounds are located in the exopolysaccharide matrix and constitute the first line of defense against UV penetration and subsequent damage [11,12,13]. Scytonemin a lipid soluble and yellow-brown pigment exclusively found some cyanobacteria [11] This compound is is a dimer composed ofof indolic and phenolic subunits cyanobacteria. Maximum absorption at 384 nm [11,22]
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