Enhancing cyclotide bioproduction: harnessing biological synthesis methods and various expression systems for...

Peptide-based medications hold immense potential in addressing a wide range of human disorders and discomforts. However, their widespread utilization encounters two major challenges: preservation and production efficiency. Cyclotides, a class of ribosomally synthesized and post-translationally modified peptides (RiPPs), exhibit unique characteristics, such as a cyclic backbone and cystine knot, enhancing their stability and contributing to a wide range of pharmacological properties exhibited by these compounds. Cyclotides are efficient in the biomedical (e.g., antitumor, antidiabetic, antimicrobial, antiviral) and agrochemical fields by exhibiting activity against pests and plant diseases. Furthermore, their structural attributes make them suitable as molecular scaffolds for grafting and drug delivery. Notably, the mutated variant of kalata B1 cyclotide ([T20K] kalata B1) has recently entered phase 1 of human clinical trials for multiple sclerosis, building upon the success observed in animal trials. To enable large-scale production of cyclotides, it is crucial to further explore their remarkable structural and bioactive properties. This necessitates extensive research focused on enhancing the efficiency of the processes required for their production. This study provides a comprehensive review of the biological synthesis methods of cyclotides, with particular emphasis on various expression systems, namely bacteria, plants, yeast, and cell-free systems. By investigating these expression systems, it becomes possible to design production systems that are adaptable, economically viable, and efficient for generating active and pure cyclotides at an industrial scale. The advantages of biological synthesis over chemical synthesis are thoroughly explored, highlighting the potential of these expression systems in meeting the demands of large-scale cyclotide production.