A Novel hGHRH Analog and its Comparative Activity

Song-Shan      Tang; Ming-Hua      Du; Xiao-Wen      Zhang; Juan-Hui      Zhang; Jie      Wu; Esam      Mahanmad; Jing-Jing      Liu

Abstract

Growth hormone releasing hormone is one of the hormones secreted from the hypothalamus. Because of its potential applications in agriculture and medicine, its short half-life and its expensive chemical synthesis, an analog with high GHRH activity and prolonged half-life was sought after. The fusion partner gene with 127 amino acid residues of the C-terminus from L-asparaginase was recombined with asp-pro-hGHRH(1-44) gene synthesized by PCR method to form one kind of fusion protein with unique acid labile linker Asp-Pro. The Pro-hGHRH(1-44) peptide was purified to homogeneity by means of cell disruption, washing, ethanol precipitation, acid hydrolysis, SP-Sephadex C-25, and Sephadex G-10 column chromatography. The peptides molecular weight of 5,139 Da as measured by EIS-MS was coincident with the actual values. In the study of the activity, the doses of peptide were 0.1, 1.0, and 10 g/μl for rat pituitary and 5 g/μl for human pituitary. The peptide increased GH releases from rat pituitary in a concentrationdependent manner (P < 0.05; P < 0.01). At 1.0 g/ml, there was a significant difference between Pro-Pro-hGHRH(1-44)- Gly-Gly-Cys and Pro-hGHRH(1-44) or Pro-Pro-hGHRH(1-44) (P < 0.05), whereas the standard hGHRH(1-40) showed no measured rGH release. For human fetal pituitary, the Pro-hGHRH(1-44) peptides showed good GH-releasing activity, but there were no significant differences between them. The structure-activity relationship showed that for both rat and human fetal pituitary, the net GH-releasing activity of the Pro-hGHRH(1-44) analog was more than that of Pro-Pro-hGHRH(1- 44). The results of the other hormones from human pituitary showed that the analog had good function-selectivity and species specificity.

Keywords: Neuropeptide, growth hormone releasing hormone analog, structure-activity relationship, peptide fusion expression, pituitary hormone, species specificity, growth hormone

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