Characterisation of novel metabolically-stable peptides from chenopodium quinoa

• Main Author: Ng, Jaclyn Cheah Yee
• Other Authors: James P Tam
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2018
• Subjects: DRNTU::Science::Biological sciences::Biochemistry
• Online Access: http://hdl.handle.net/10356/74164
• Institution: Nanyang Technological University

Hevein-like peptides are cysteine-rich, chitin-binding peptides often involved in plant anti- microbial defence. They vary between 2-6 kDa in size and characteristically contain 6-10 cysteine residues. The remarkable stability conferred by multiple disulfide crosslinks is hypothesised to contribute to the preservation of biological activity in consumed herbs, which also makes hevein-like peptides highly-attractive candidates for drug development. This study reports the discovery and characterisation of three novel 6C-hevein- like peptides, termed “chenotides”, from Chenopodium quinoa. The chenotides were purified using a combination of C18 flash chromatography, strong cationic exchange chromatography and reverse-phase high-performance liquid chromatography. They were found to be 29-31 amino acids in length, with a conserved chitin-binding motif. NMR analysis revealed a secondary structure comprising two short anti-parallel β-strands and an α-helix-like motif, supported by disulfide linkages arranged in a cystine knot. Genomic analysis revealed a three-domain structure indicative of a secretory peptide, as well as two identical tandem repeats in the mature domain. The chenotides demonstrated strong affinity to chitin, resistance against heat, acidic and enzymatic degradation, as well as non-cytotoxicity against HeLa and HUVEC cells. These chenotides represent the first 6C-hevein- like peptides discovered to contain identical tandem repeats, with results indicating good potential for development into orally- active therapeutics.