Expression of a glucagon-like peptide-1 analogue, as a therapeutic agent for type II diabetes, with enhanced bioactivity and increased N-terminal homogeneity in Pichia pastoris.

Abstract

To improve the bioactivity and increase the N-terminal homogeneity of a glucagon-like peptide-1 (GLP-1) analogue expressed in Pichia pastoris. The GLP-1 analogue. GGH, consisting of two tandem mutant GLP-1 (GLP-1[A2G]) fused with the N-terminus of human serum albumin (HSA), was expressed in P. pastoris. We also designed and expressed the novel GLP-1 analogue NGGH, which had a His-tag fused with the N-terminus of GGH and an enterokinase (EK) cleavage site at the fusion junction. The His-tag was removed by EK digestion to yield GGH2, which was subsequently compared with GGH expressed in P. pastoris. The purification recovery of GGH2 was 35% compared with 23% for GGH. Furthermore, the bioactivity of GGH2 was 605% higher than GGH, and N-terminal homogeneity was also improved. A simple method for the preparation of GGH2 with a cleavable His-tag was developed, and the resultant protein possessed improved bioactivity and N-terminal homogeneity.