Identification and characterization of a wolfberry carboxypeptidase inhibitor from Lycium barbarum

• Main Authors: Huang, Jiayi, Wong, Ka Ho, Tan, Wei Liang, Tay, Stephanie Victoria, Wang, Shujing, Tam, James P.
• Other Authors: School of Biological Sciences
• Format: Article
• Language: English
• Published: 2021
• Subjects: Science; Carboxypeptidase Inhibitor; Wolfberry
• Online Access: https://hdl.handle.net/10356/148027
• Institution: Nanyang Technological University

Hyperstable cysteine-rich peptides (CRPs) represent an underexplored superfamily of bioactives in functional foods. An example is wolfberry of the Lycium barbarum family. Previously, we discovered a CRP, designated α-lybatide, from L. barbarum bark. Herein, we report the discovery of β-lybatide, a novel carboxypeptidase inhibitor belonging to a different CRP family from the wolfberry plant. Proteomic and transcriptomic analyses showed that β-lybatide contains 36 amino acids with six cysteine residues. NMR spectroscopy revealed that β-lybatide displays a knottin-like structure that renders it highly resistant to thermal, chemical and enzymatic degradation, conditions important for keeping its structural integrity in gastrointestinal tract. Biochemical assays showed that β-lybatide is a potent carboxypeptidase inhibitor which could contribute to the wolfberry biological activities. Bioinformatics analysis revealed an additional 49 β-lybatide-like plant carboxypeptidase inhibitors. Together, our results show that β-lybatide is the first and the smallest plant-derived hyperstable carboxypeptidase inhibitor discovered from a functional food.