Gene cloning and expression of a novel hypoglycaemic peptide from Momordica charantia

Momordica charantia (MC) is used in many Asian countries as a traditional functional food and medicine. Polypeptide-P, a 166 amino acid (AA) polypeptide isolated from MC seeds, has been reported to show hypoglycaemic effects in patients with type I or type II diabetes. The AA sequence of this peptide has been determined, but its gene sequence has yet to be published.

In this study a gene-cloning strategy was employed to obtain the polypeptide-P gene sequence using degenerate reverse transcription polymer chain reaction and genome-walking methods. A complete 498 bp sequence encoding the polypeptide-P protein was cloned from MC seeds. Subsequent assays of the bioactivity of the expressed recombinant protein revealed that it had significant hypoglycaemic activity in alloxan-induced diabetic mice. This result suggests that recombinant polypeptide-P has hypoglycaemic effects.

This is the first report of cloning and expression of the MC polypeptide-P gene. The cloned gene could be helpful for exploring the mechanisms of polypeptide-P gene expression and regulation in MC. Furthermore, this gene could be used as a potential tool both for screening MC varieties with high hypoglycaemically active substance content and for breeding new varieties of MC with high economic value, which could in turn be beneficial to farmers.