Abstract
Cyanobacteria of the genus Nostoc are widespread in all kinds of habitats. They occur in a free-living state or in association with other organisms. Members of this genus belong to prolific producers of bioactive metabolites, some of which have been recognized as potential therapeutic agents. Of these, peptides and peptide-like structures show the most promising properties and are of a particular interest for both research laboratories and pharmaceutical companies. Nostoc is a sole source of some lead compounds such as cytotoxic cryptophycins, antiviral cyanovirin-N, or the antitoxic nostocyclopeptides. Nostoc also produces the same bioactive peptides as other cyanobacterial genera, but they frequently have some unique modifications in the structure. This includes hepatotoxic microcystins and potent proteases inhibitors such as cyanopeptolins, anabaenopeptins, and microginins. In this review, we described the most studied peptides produced by Nostoc, focusing especially on the structure, the activity, and a potential application of the compounds.
Highlights
Cyanobacteria, the photosynthetic Gram-negative bacteria, are one of the oldest forms of life onEarth
A significant part of the metabolites produced by Nostoc belongs to nonribosomal peptides (NRPs) or polyketides (PKs)
MHEA is 2-methylhex-2-enoic acid, O-MeSer is O-methylated serine, PhePr is phenylalanylpropanoic acid, Dhb is dehydrobutyric acid, and Hyp is hydroxyproline (Figure 2) [94]. As it could be concluded from the presence of non-proteinogenic amino acid residues in the structures, Nps belong to Non-Ribosomal Peptides (NRPs) and are assembled through a mixed non-ribosomal peptide synthetases (NRPS)/polyketide synthases (PKS) biosynthetic pathway [96]
Summary
Cyanobacteria, the photosynthetic Gram-negative bacteria, are one of the oldest forms of life on. A significant part of the metabolites produced by Nostoc belongs to nonribosomal peptides (NRPs) or polyketides (PKs). They are characterized by a structural diversity and a broad spectrum of biological activities, including cytotoxic [36], enzyme inhibiting [37], anti-inflamatory [38], antibacterial [39], and antifungal effects [40]. The ability to produce NRPs and PKs is a strain-specific feature, and in an individual strain, several classes of the compounds can be found These compounds have linear, cyclic, or branched cyclic structure and are composed of proteogenic and non-proteogenic amino acids. We focus mainly on the peptides produced solely by the genus Nostoc, but some examples of the peptides occurring in other cyanobacterial taxa are discussed as well
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