Shared biosynthetic architectures generate diverse β-amino polyketide residues in cyanobacterial peptides

Abstract

Cyanobacteria generate structurally complex peptides with diverse biological functions and vast chemical diversity, yet the enzymatic logic that produces their many documented unusual {beta}-amino acid-containing polyketide units remains incompletely understood. Here we show that the recently described genus Floridanema harbors biosynthetic systems that unify the production of tychonamides and pahayokolide-like peptides, including the assembly of the signature residues 3-amino-2,5,7-trihydroxy-8-phenyloctanoic acid (Atpoa) and 3-amino-2,5,7,8-tetrahydroxy-10-methylundecanoic acid (Athmu). Using an integrated "pathways-to-products" strategy combining comparative genomics, bioinformatics analyses, and structure elucidation by NMR and MS, we link previously cryptic gene clusters to new metabolites and define shared architectural features across these pathways. Furthermore, we identified a ketoreductase in multiple pathways predicted to reduce -keto acids and generate the starting unit in the Athmu moiety. These results support a common evolutionary origin or convergent phenomenon for constructing {beta}-amino polyketide building blocks within cyanobacterial hybrid assembly lines. Together, our findings reposition Floridanema as a central source organism for these peptide families and establish biosynthetic principles that can be leveraged to predict, discover, and engineer related natural products. Significance StatementCyanobacteria produce unusually complex peptides, but the enzymatic logic that builds their signature {beta}-amino polyketide residues is poorly understood. By linking gene clusters identified in the genomes of members of the recently described Floridanema genus to the production of tychonamides, pahayokolide-like peptides, and other metabolites, we reveal shared biosynthetic architectures and suggest evolutionary strategies that drive peptide diversification.