Peptoid-based Positional Scanning Derivatives: Revealing the Optimum Residue Required for Ice Recrystallization Inhibition Activity for Every Position in the AFGPs

摘要

Antifreeze glycoproteins (AFGPs) bind to the ice crystals, thereby inhibit ice crystal growth. The discovery of AFGPs in the blood serum of fish by De Vries demonstrated that AFGPs is an essential biomaterial for fish to survive at subzero temperature in the Antarctic Sea. This unique property of AFGPs has attracted significant interest due to their potential application in a variety of fields including medicine and the frozen-food industry. AFGPs were classified into 8 subclasses, in which AFGP1 has the largest (33.7 kDa), and AFGP8 has the lowest molecular weight fraction (2.6 kDa). Among AFGPs, AFGPS is a good candidate as biomaterial due to the lowest molecular weight (2.6 kDa) that led to the intensive studies on the synthesis and activity of AFGP8-related compounds by several research groups, to develop efficient and cost-effective mass production of AFGPs with high purity as well as to understand the mechanism of action of AFGP8. AFGP8 was consists of repeating tripeptide units, Alanyl-Alanyl-Threonyl (Ala-Ala-Thr)_(n=4) units, connected with the disaccharide P-D-galactosyl-(l→3)-α-D-N-acetyl-galactosamine through a glycosidic bond at the hydroxyl group of the threonine residue. Although AFGP8 is a good candidate for the medical and industrial applications, one of the greatest huddles has been to achieve stability. As a part of our continuing efforts toward the rational design of AFGP mimics possessing enhanced stability, we have developed a low-cost synthetic strategy to afford simple structural mimics of AFGP8. Our approach utilized the peptoids, or N-sub-stituted oligoglycines in which sugar moiety is moved into the amide nitrogen atom from the α-carbon atom of each threonine residue. Peptoid bond is well known to have a more resistant proteolytic degradation and enhance the cell permeability compare to natural peptide bond. We prepared a series of AFGP8 analogues by incorporating glyco-peptoid monomer (P) and carried out the positional scanning in order to figure out the distinct position of peptoid mimics in the native AFGP with either increase or retain in activity.