Subtopic Deep Dive
Cyclotide Macrocyclization and Stability
Research Guide
What is Cyclotide Macrocyclization and Stability?
Cyclotide macrocyclization and stability refers to the head-to-tail backbone cyclization and cysteine knot motifs that provide proteolytic resistance to plant-derived cyclotides, enabling their use as stable peptide scaffolds.
Cyclotides feature a cyclic peptide backbone stabilized by a cystine knot of three disulfide bonds. Research examines biosynthetic enzymes like asparaginyl endopeptidase for cyclization and NMR/molecular dynamics for folding pathways. Over 20 papers from 2005-2023, including Harris et al. (2015, 251 citations) and Nguyen et al. (2015, 175 citations), detail enzymatic and chemical strategies.
Why It Matters
Cyclotide stability supports engineering stable peptide therapeutics targeting extracellular proteins, as scaffolds resist proteolysis (Wang et al., 2022, 1762 citations). Enzymatic macrocyclization using butelase 1 or asparaginyl endopeptidase enables efficient production of cyclized variants for drug development (Nguyen et al., 2015; Harris et al., 2015). Databases like CyBase facilitate discovery and engineering of cyclotide sequences for agriculture and medicine (Wang et al., 2007, 288 citations; Oguis et al., 2019, 215 citations).
Key Research Challenges
Enzyme Efficiency Variability
Recombinant asparaginyl endopeptidase achieves efficient backbone cyclization but substrate specificity limits yields for engineered variants (Harris et al., 2015). Butelase 1 offers versatility yet requires optimization for diverse sequences (Nguyen et al., 2015). Scalability remains hindered by plant-derived enzyme heterogeneity.
Folding Pathway Prediction
Cystine-knot formation involves complex oxidative folding pathways difficult to predict without NMR or dynamics simulations (Reinwarth et al., 2012). Combinatorial optimization of cystine-knot peptides reveals stability trade-offs during folding (Glotzbach et al., 2013). Accurate modeling demands high computational resources.
Sequence Engineering Stability
Grafting sequences into cyclotide scaffolds disrupts knot integrity, reducing proteolytic resistance (Wang et al., 2007). Chemical synthesis enables cyclization but oxidative folding yields vary (Reinwarth et al., 2012). Balancing affinity and stability in variants challenges therapeutic design.
Essential Papers
Therapeutic peptides: current applications and future directions
Lei Wang, Nanxi Wang, Wenping Zhang et al. · 2022 · Signal Transduction and Targeted Therapy · 1.8K citations
Abstract Peptide drug development has made great progress in the last decade thanks to new production, modification, and analytic technologies. Peptides have been produced and modified using both c...
New developments in RiPP discovery, enzymology and engineering
Manuel Montalbán‐López, Thomas Allan Scott, Sangeetha Ramesh et al. · 2020 · Natural Product Reports · 733 citations
This review provides a comprehensive update of the advances in discovery, biosynthesis, and engineering of ribosomally-synthesized and post-translationally modified peptides (RiPPs).
Cyclic Peptides for Drug Development
Xinjian Ji, Alexander L. Nielsen, Christian Heinis · 2023 · Angewandte Chemie International Edition · 295 citations
Abstract Cyclic peptides are fascinating molecules abundantly found in nature and exploited as molecular format for drug development as well as other applications, ranging from research tools to fo...
CyBase: a database of cyclic protein sequences and structures, with applications in protein discovery and engineering
Conan K. Wang, Quentin Kaas, L. Chiche et al. · 2007 · Nucleic Acids Research · 288 citations
CyBase was originally developed as a database for backbone-cyclized proteins, providing search and display capabilities for sequence, structure and function data. Cyclic proteins are interesting be...
Cyclic peptide drugs approved in the last two decades (2001–2021)
Huiya Zhang, Shiyu Chen · 2021 · RSC Chemical Biology · 281 citations
In this mini-review, we summarized the chemical structure, mechanism of action, and metabolism of cyclic peptide drugs approved in the last two decades. We also examined factors important for the d...
Efficient backbone cyclization of linear peptides by a recombinant asparaginyl endopeptidase
Karen S. Harris, Thomas Durek, Quentin Kaas et al. · 2015 · Nature Communications · 251 citations
Abstract Cyclotides are diverse plant backbone cyclized peptides that have attracted interest as pharmaceutical scaffolds, but fundamentals of their biosynthetic origin remain elusive. Backbone cyc...
Peptides and Peptidomimetics for Antimicrobial Drug Design
Biljana Mojsoska, Håvard Jenssen · 2015 · Pharmaceuticals · 221 citations
The purpose of this paper is to introduce and highlight a few classes of traditional antimicrobial peptides with a focus on structure-activity relationship studies. After first dissecting the impor...
Reading Guide
Foundational Papers
Start with Wang et al. (2007, CyBase database, 288 citations) for cyclotide sequence/structure catalog, then Harris et al. (2015) for biosynthetic cyclization mechanism, establishing stability motifs.
Recent Advances
Study Ji et al. (2023, 295 citations) on cyclic peptide drug formats and Wang et al. (2022, 1762 citations) for therapeutic applications highlighting cyclotide scaffolds.
Core Methods
Enzymatic macrocyclization (asparaginyl endopeptidase, butelase 1), chemical synthesis with oxidative folding, NMR/molecular dynamics for knot analysis, CyBase for sequence mining.
How PapersFlow Helps You Research Cyclotide Macrocyclization and Stability
Discover & Search
Research Agent uses searchPapers to retrieve Harris et al. (2015) on asparaginyl endopeptidase cyclization, then citationGraph maps 250+ citing works on enzymatic stability, and findSimilarPapers uncovers Nguyen et al. (2015) butelase methods.
Analyze & Verify
Analysis Agent applies readPaperContent to parse folding data from Reinwarth et al. (2012), verifies stability claims via verifyResponse (CoVe) against NMR metrics, and runs PythonAnalysis with NumPy/pandas to quantify disulfide bond probabilities across 10 cyclotide structures, graded by GRADE for evidence strength.
Synthesize & Write
Synthesis Agent detects gaps in butelase substrate engineering via gap detection, flags contradictions between chemical vs. enzymatic yields, then Writing Agent uses latexEditText and latexSyncCitations to draft stability comparison tables, with latexCompile exporting polished manuscripts.
Use Cases
"Analyze disulfide bond statistics in cyclotide folding pathways from top 10 papers"
Research Agent → searchPapers → Analysis Agent → runPythonAnalysis (pandas/matplotlib on extracted NMR data) → matplotlib plots of knot stability metrics.
"Write LaTeX review comparing butelase vs. asparaginyl endopeptidase for macrocyclization"
Synthesis Agent → gap detection → Writing Agent → latexEditText + latexSyncCitations (Harris 2015, Nguyen 2015) → latexCompile → PDF with cyclization yield tables.
"Find GitHub repos with cyclotide simulation code linked to recent papers"
Research Agent → citationGraph (Wang 2022) → Code Discovery (paperExtractUrls → paperFindGithubRepo → githubRepoInspect) → molecular dynamics scripts for stability analysis.
Automated Workflows
Deep Research workflow scans 50+ cyclotide papers via searchPapers → citationGraph, generating structured reports on macrocyclization enzymes with GRADE-verified stability data. DeepScan applies 7-step analysis with CoVe checkpoints to validate folding claims in Reinwarth et al. (2012). Theorizer generates hypotheses on butelase engineering from Nguyen et al. (2015) and Harris et al. (2015).
Frequently Asked Questions
What defines cyclotide macrocyclization?
Head-to-tail backbone cyclization by asparaginyl endopeptidase or butelase 1 forms the cyclic structure stabilized by cystine knot (Harris et al., 2015; Nguyen et al., 2015).
What are key methods for cyclotide stability?
Enzymatic ligation with butelase 1 or recombinant asparaginyl endopeptidase, plus chemical synthesis and oxidative folding for cystine-knot formation (Nguyen et al., 2015; Reinwarth et al., 2012).
What are landmark papers?
Harris et al. (2015, 251 citations) on asparaginyl endopeptidase; Wang et al. (2007, 288 citations) CyBase database; Nguyen et al. (2015, 175 citations) butelase 1.
What open problems exist?
Improving enzyme substrate range for variant cyclization, predicting folding yields computationally, and scaling production without losing knot stability (Harris et al., 2015; Glotzbach et al., 2013).
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