The invention provides a novel oral
blood sugar reducing polypeptide. The polypeptide is an improved derivative based on Exendin-4. According to the present invention, the Exendin-4 is analyzed so as to obtain the core sequence of 28 amino acids, wherein the core sequence is HGEGTFTSDLSKQMEEEAVRLFIEWLKN; in order to improve the stability and
bioavailability, four key sites are subjected to
amino acid substitution (K12H, R20H, F22A and K27H), AF and FK are respectively added at the N end and the C end, and finally a
complete sequence with 32 amino acids is formed. The structural modifications significantly improve the oral
absorption efficiency of the polypeptide. Compared with an Exendin-4 prototype, the antihyperglycemic polypeptide Ex32 disclosed by the invention has the advantages that the enzymolysis resistance is obviously improved, and the obtained Ex32-containing polypeptide has good physical and
chemical stability and
bioavailability and can be directly used for preparing various dosage forms, for example, the Ex32-containing polypeptide can be used for treating
type II diabetes mellitus.