Polyketides such as the antibiotic erythromycin or the immunosuppressant rapamycin, and non-ribosomal peptides, such as the antibiotics penicillin or vancomycin, are important classes of natural products. The core of these molecules are biosynthesized by large polyketide synthases (PKS) and non-ribosomal peptide synthetases (NRPS), respectively. The modular architecture of these enzymatic assembly lines makes them interesting candidates for synthetic biology approaches. The re-engineering efforts aim to understand the molecular structure, produce new compounds, produce analogs of known compounds, tag the products or improve activity and/or yield. Here, we first consider the definition of PKS and NRPS modules, then give an overview of different strategies for re-engineering and finally review recent examples of PKS and NRPS reengineering.

Recent Advances in Re-engineering Modular PKS and NRPS Assembly Lines

https://doi.org/10.1016/j.synbio.2022.01.007

Complex peptide natural products: Biosynthetic principles, challenges and opportunities for pathway engineering

https://pubs.rsc.org/en/content/articlepdf/2021/np/d1np00019e

Ribosome-independent peptide biosynthesis: the challenge of a unifying nomenclature.

Ribosome-independent peptide biosynthesis: the challenge of a unifying nomenclature

Nonribosomal peptide synthetases (NRPSs) are a vast source of valuable natural products, and re-engineering them is an attractive path toward structurally diversified active compounds. NRPS engineering often requires heterologous expression, which is hindered by the enormous size of NRPS proteins. Protein splitting and docking domain insertion have been proposed as a strategy to overcome this limitation. Here, we have applied the splitting strategy to the gramicidin S NRPS: Despite better production of the split proteins, gramicidin S production almost ceased. However, the addition of type II thioesterase GrsT boosted production. GrsT is an enzyme encoded in the gramicidin S biosynthetic gene cluster that we have produced and characterized for this purpose. We attribute the activity enhancement to the removal of a stalled intermediate from the split NRPS that is formed due to misinitiation. These results highlight type II thioesterases as useful tools for NRPS engineering.

https://pubs.acs.org/doi/pdf/10.1021/acschembio.2c00341

Proof-Reading Thioesterase Boosts Activity of Engineered Nonribosomal Peptide Synthetase

Non-ribosomal peptide synthetases (NRPSs) are the origin of a wide range of natural products, including many clinically used drugs. Efficient engineering of these often-giant biosynthetic machineries to produce novel non-ribosomal peptides (NRPs) is an ongoing challenge. Here we describe a cloning and co-expression strategy to functionally combine NRPS fragments of Gram-negative and -positive origin, synthesising novel peptides at titres up to 220 mg l -1 . Extending from the recently introduced definition of e X change U nits (XUs), we inserted synthetic zippers (SZs) to split single protein NRPSs into independently expressed and translated polypeptide chains. These synthetic type of NRPS (type S) enables easier access to engineering, overcomes cloning limitations, and provides a simple and rapid approach to building peptide libraries via the combination of different NRPS subunits.

Synthetic Zippers as an Enabling Tool for Engineering of Non-Ribosomal Peptide Synthetases*.

Non-ribosomal peptide synthetases (NRPSs) are the origin of a wide range of natural products, including many clinically used drugs. Engineering of these often giant biosynthetic machineries to produce novel non-ribosomal peptides (NRPs) at high titre is an ongoing challenge. Here we describe a strategy to functionally combine NRPS fragments of Gram-negative and -positive origin, synthesising novel peptides at titres up to 290 mg l-1. Extending from the recently introduced definition of eXchange Units (XUs), we inserted synthetic zippers (SZs) to split single protein NRPSs into up to three independently expressed and translated polypeptide chains. These synthetic type of NRPS (type S) enables easier access to engineering, overcomes cloning limitations, and provides a simple and rapid approach to building peptide libraries via the combination of different NRPS subunits. One Sentence Summary Divide and Conquer: A molecular tool kit to reprogram the biosynthesis of non-ribosomal peptides.

/pdf/synthetic-zippers-as-an-enabling-tool-for-engineering-of-non-25gm8s4a40.pdf

Synthetic Zippers as an Enabling Tool for Engineering of Non-Ribosomal Peptide Synthetases

A Practical Guideline to Engineering Nonribosomal Peptide Synthetases.

Bacterial biosynthetic assembly lines, such as non-ribosomal peptide synthetases (NRPS) and polyketide synthases, are often subject of synthetic biology – because they produce a variety of natural products invaluable for modern pharmacotherapy. Acquiring the ability to engineer these biosynthetic assembly lines allows the production of artificial non-ribosomal peptides (NRP), polyketides, and hybrids thereof with new or improved properties. However, traditional bioengineering approaches have suffered for decades from their very limited applicability and, unlike combinatorial chemistry, are stigmatized as inefficient because they cannot be linked to the high-throughput screening platforms of the pharmaceutical industry. Although combinatorial chemistry can generate new molecules cheaper, faster, and in greater numbers than traditional natural product discovery and bioengineering approaches, it does not meet current medical needs because it covers only a limited biologically relevant chemical space. Hence, methods for high-throughput generation of new natural product-like compound libraries could provide a new avenue towards the identification of new lead compounds. To this end, prior to this work, we introduced an artificial synthetic NRPS type, referred to as type S NRPS, to provide a first-of-its-kind bicombinatorial approach to parallelized high-throughput NRP library generation. However, a bottleneck of these first two generations of type S NRPS was a significant drop in production yields. To address this issue, we applied an iterative optimization process that enabled titer increases of up to 55-fold compared to the non-optimized equivalents, restoring them to wild-type levels and beyond.

/pdf/guidelines-for-optimizing-type-s-non-ribosomal-peptide-1rbozfnb.pdf

Guidelines for Optimizing Type S Non-Ribosomal Peptide Synthetases

Bacterial natural products in general, and non-ribosomally synthesized peptides in particular, are structurally diverse and provide us with a broad range of pharmaceutically relevant bioactivities. Yet, traditional natural product research suffers from rediscovering the same scaffolds and has been stigmatised as inefficient, time-, labour-, and cost-intensive. Combinatorial chemistry, on the other hand, can produce new molecules in greater numbers, cheaper and in less time than traditional natural product discovery, but also fails to meet current medical needs due to the limited biologically relevant chemical space that can be addressed. Consequently, methods for the high throughput generation of new-to-nature natural products would offer a new approach to identifying novel bioactive chemical entities for the hit to lead phase of drug discovery programms. As a follow-up to our previously published proof-of-principle study on generating bipartite type S non-ribosomal peptide synthetases (NRPSs), we now envisaged the de novo generation of non-ribosomal peptides (NRPs) on an unreached scale. Using synthetic zippers, we split NRPS in up to three subunits and rapidly generated different bi- and tripartite NRPS libraries to produce 49 peptides, peptide derivatives, and de novo peptides at good titres up to 145 mgL-1. A further advantage of type S NRPSs not only is the possibility to easily expand the created libraries by re-using previously created type S NRPS, but that functions of individual domains as well as domain-domain interactions can be studied and assigned rapidly.

https://www.biorxiv.org/content/biorxiv/early/2021/10/26/2021.10.25.465728.full.pdf

Nadya Abbood

Papers

Synthetic Zippers as an Enabling Tool for Engineering of Non-Ribosomal Peptide Synthetases*.

Synthetic Zippers as an Enabling Tool for Engineering of Non-Ribosomal Peptide Synthetases

A Practical Guideline to Engineering Nonribosomal Peptide Synthetases.

Guidelines for Optimizing Type S Non-Ribosomal Peptide Synthetases

Type S Non Ribosomal Peptide Synthetases for the rapid generation of tailor-made peptide libraries