The Antifreeze and Cryoprotective Activities of a Novel Antifreeze Peptide from Ctenopharyngodon idella Scales

Trash to treasure: Potential antifreeze peptide from Litopenaeus vannamei head via ultrasound-assisted autolysis

This study aimed to separate and purify antifreeze peptides (AFP) from the autolysate of Litopenaeus vannamei head, and the peptide sequences with antifreeze activity were identified to elucidate the potential antifreeze mechanisms. The initial fractionation of autolysate revealed that the pk1 fraction with less than 3 kDa molecular weight exhibited the highest thermal hysteresis activity (2.28 °C). Notably, the component pk1-A with the strongest antifreeze activity (2.80 °C) was further separated by using a Sephadex G-15 gel filtration column. The results of bioinformatics and computer-assisted techniques indicated that 26 types of peptides from pk1-A were identified as AFP. Among these, KQVHPDTGISSK was selected as a potential Litopenaeus vannamei head antifreeze peptide (LvAFP). The active site (Lys residue) of LvAFP was discovered to strongly interact with water molecules via hydrogen bonding, thereby inhibiting the formation and recrystallization of ice crystals. Therefore, the preparation of LvAFP could improve the high-value utilization of shrimp byproducts.

Expanding the cryoprotectant toolbox in biomedicine by multifunctional antifreeze peptides

The global cryopreservation market size rises exponentially due to increased demand for cell therapy-based products, assisted reproductive technology, and organ transplantation. Cryoprotectants (CPAs) are required to reduce ice-related damage, osmotic cell injury, and protein denaturation. Antioxidants are needed to hamper membrane lipid peroxidation under freezing stress, and antibiotics are added to the cryo-solutions to prevent contamination. The vitrification process for sized organs requires a high concentration of CPA, which is hardly achievable using conventional penetrating toxic CPAs like DMSO. Antifreeze peptides (AFpeps) are biocompatible CPAs leveraging inspiration from nature, such as freeze-tolerant and freeze-avoidant organisms, to circumvent logistic limitations in cryogenic conditions. This study aims to introduce the advances of AFpeps with cell-penetrating, antioxidant, and antimicrobial characteristics. We herein revisit the placement of AFpeps in the biobanking of cancer cells, immune cells, stem cells, blood cells, germ cells (sperms and oocytes), and probiotics. Implementing low-immunogenic AFpeps for allograft cryopreservation minimizes HLA mismatching risk after organ transplantation. Applying AFpeps to formulate bioinks with optimal rheology in extrusion-based 3D cryobiopriners expedites the bench-to-beside transition of bioprinted scaffolds. This study advocates that the fine-tuned synthetic or insect-derived AFpeps, forming round blunt-shape crystals, are biomedically broad-spectrum, and cell-permeable AFpeps from marine and plant sources, which result in sharp ice crystals, are appropriate for cryosurgery. Perspectives of the available room for developing peptide mimetics in favor of higher activity and stability and peptide-functionalized nanoparticles for enhanced delivery are delineated. Finally, antitumor immune activation by cryoimmunotherapy as an autologous in-vivo tumor lysate vaccine has been illustrated.

Peptidomics & Molecular Simulation-Based Specific Screening of Antifreeze Peptides from Evynnis japonica Scale and the Action Mechanism

This study aims to explore the cryoprotective mechanisms of food-derived hydrolyzed peptides and develop novel cryoprotectants to enhance the quality of frozen foods. Evynnis japonica scale antifreeze peptides (Ej-AFP) were prepared using enzymatic hydrolysis, which had a 4-fold increase in protection efficiency for surimi compared to traditional cryoprotectants. Furthermore, Ej-AFP was able to control 63.60% of the ice crystals to sizes below 600 μm2. Three antifreeze peptide sequences were purified by using ice-affinity techniques and peptidomics. These sequences demonstrated a 21.75% enhancement in antifreeze activity and an increase of 1 °C in thermal hysteresis activity compared to Ej-AFP. Molecular simulation-elucidated ice-binding surface interacts with ice crystals through hydrogen bonds, while the nonice-binding surface disrupts the orderly arrangement of water molecules. This results in a tightly structured hydration layer around the peptide, increasing the curvature of the ice crystal surface and thereby demonstrating significant antifreeze activity in controlling ice crystal growth.

Insight into the structure-activity relationship of thermal hysteresis activity of cod collagen peptides through peptidomics and bioinformatics approaches

To elucidate the correlation between variations in thermal hysteresis activity (THA) and the physicochemical properties and structure, antifreeze peptides (AFPs) of isolated fractions (CCP-1 and CCP-2) were characterized on based peptidomics and bioinformatics. The results revealed a positive correlation between the THA of cod collagen antifreeze peptide (CCAFP) and peptide chain length, isoelectric point, and hydrophobic amino acid content. Notably, the THA of CCP-1, which has higher alkaline amino acid content, was 2.60 °C at a concentration of 10 mg/mL, significantly higher than CCP (1.90 °C) and CCP-2 (2.27 °C). Glycine, proline, and valine were the vital amino acids to the formation of hydrogen bonds. Conversely, aspartic and glutamic acids at terminal regions of AFPs tended to introduce kinks in their structures. This distortion reduced binding sites for ice crystals, thereby decreasing their THA, providing a theory for understanding the physicochemical properties and structure of AFPs that influence their THA.

Recent Advances in Antifreeze Peptide Preparation: A Review

Antifreeze agents play a critical role in various fields including tissue engineering, gene therapy, therapeutic protein production, and transplantation. Commonly used antifreeze agents such as DMSO and other organic substances are known to have cytotoxic effects. Antifreeze proteins sourced from cold-adapted organisms offer a promising solution by inhibiting ice crystal formation; however, their effectiveness is hindered by a dynamic ice-shaping (DIS) effect and thermal hysteresis (TH) properties. In response to these limitations, antifreeze peptides (AFPs) have been developed as alternatives to antifreeze proteins, providing similar antifreeze properties without the associated drawbacks. This review explores the methods for acquiring AFPs, with a particular emphasis on chemical synthesis. It aims to offer valuable insights and practical implications to drive the realm of sub-zero storage.

The cryoprotective effect of Litopenaeus vannamei head-derived peptides and its ice-binding mechanism

Although discarded as waste, shrimp heads are a potential source of antifreeze peptides, which can be used as cryoprotectants in the food industry. Their utilization in frozen foods can help mitigate the negative effects caused by the freezing technique. Litopenaeus vannamei shrimp heads were autolyzed, and the shrimp head autolysate (SHA) was separated via ultra-filtration and ion exchange chromatography. The antifreeze effect of SHA on the biochemical properties of myofibrillar proteins of peeled shrimps during five freeze-thaw cycles was evaluated. Peptide screening was done using the LC-MS/MS technique. A molecular docking (MD) study of the interaction between ice and shrimp head-derived antifreeze peptides was done. Results showed that shrimp-head autolysate has a maximum thermal hysteresis value of 1.84 °C. During the freeze-thaw cycles, the shrimp-head autolysate exhibited an antifreeze effect on frozen peeled shrimps. 1.0 and 3.0%-SHA groups showed significantly lower freeze denaturation than the negative control group. The muscle tissues of SHA-treated groups were not as severely damaged as the negative control group. The molecular docking study revealed that the shrimp head-AFPs bound to ice via hydrogen bonding, and both hydrophilic and hydrophobic amino acid residues were involved in the ice-binding interactions. 6 ice-binding sites were involved in the peptide-ice interaction. Our findings suggest that shrimp head-derived AFPs can be developed into functional additives in frozen foods and add more insights into the existing literature on antifreeze peptides.