Ways of Assembling Complex Natural Products on Modular Nonribosomal Peptide Synthetases A list of abbreviations can be found at the end of the text.

Abstract

Nonribosomal peptide synthetases (NRPSs) catalyze the assembly of a large number of complex peptide natural products, many of which display therapeutically useful activity. Each cycle of chain extension is carried out by a dedicated module of the multifunctional enzymes. A module harbors all the catalytic units, which are referred to as domains, necessary for recognition, activation, covalent binding, and optionally modification of a single building block monomer, as well as for peptide-bond formation with the growing chain. A terminal domain releases the full-length peptide chain from the enzyme complex. Recent characterization of many NRPS systems revealed several examples where the sequence of the product does not directly correspond to the linear arrangement of modules and domains within the enzyme(s). It is now obvious that these systems cannot be regarded as rare exceptions of the common NRPS architecture but rather represent more complicated variations of the NRPS repertoire to increase their biosynthetic potential. In most of these cases unusual peptide structures of the products are observed, such as structures with side-chain acylation, cyclization involving the peptide backbone and/or side chains, and transfer of the peptide chain onto soluble small-molecule substrates. These findings indicate a previously unexpected higher versatility of the modules and domains in terms of both catalytic potential and interaction within the multifunctional protein templates. We propose to classify the known NRPS systems into three groups, linear NRPSs (type A), iterative NRPSs (type B), and nonlinear NRPSs (type C), according to their biosynthetic logic. Understanding the various biosynthetic strategies of NRPSs will be crucial to fully explore their potential for engineered combinatorial biosynthesis.

Spontaneity in the patellamide biosynthetic pathway

“…This process would then differ from macrocyclisation in non-ribosomal peptide synthetases, in which an enzyme-bound peptide chain is cleaved by a terminal thioesterase and cyclised under control of the same enzyme. 18 In pathway 2 a free fully tailored Asc D-Thz chain would be expected to complex to an enzyme which would activate it and enforce a conformation in which macrocyclisation is possible.…”

A 4′‐Phosphopantetheinyl Transferase Mediates Non‐Ribosomal Peptide Synthetase Activation in Aspergillus fumigatus

“…[12] (Other domain types can also be present and are reviewed elsewhere. [13] ) Each domain has a specific function: the adenylation domain recognises and adenylates, by ATP hydrolysis, a substrate amino acid, which is in turn transferred to the 4'-phosphopantetheine prosthetic group of the thiolation domain by covalent attachment to an available SH group on the 4'-phosphopantetheine moiety. Ultimately, the covalent attachment of the amino acid to a proximal amino acid occurs through the condensation domain followed by either sequential transfer within the NRPS modular system or release through thioesterase activity to yield functional, non-ribosomally synthesised peptides.…”

Fungal cyclooligomerdepsipeptides: From classical biochemistry to combinatorial biosynthesis

“…Finally, nonlinear (Type C) NRPSs feature unusual arrangements of their core domains and often incorporate precursors that are not tethered on carrier domains. 7 The tremendous structural variety of nonribosomal peptides is based on the flexibility of the biosynthetic programming of the NRPS: the utilization of non-proteinogenic amino acid precursors (more than 300 described); the formation of main-chain heterocycles (thiazole, oxazole and their derivatives); and the construction of linear, macrocyclic or branched macrocyclic structures with amide, ester or even thioester or imino ring closures. 4,8 In the scaffold of the nonribosomal depsipeptides, at least one bond of the peptide backbone is replaced by an ester bond: these connect carboxy groups of amino acids with a 2-hydroxycarboxylic acid, or provide alternative routing of the chain via side chain hydroxy groups of amino acids and the Cterminus of the peptide.…”

“…2 Heterologous production of beauvericin 7 Structural diversification of CODs 7.1 Natural COD congeners 7. 2 Unnatural CODs from precursor-directed biosynthesis 7.…”