Synthesis of ghrelin: chemical synthesis and semisynthesis for large-scale preparation of modified peptides.

Most biologically active peptide hormones, including ghrelin, undergo numerous posttranslational modifications and play many crucial roles in nature. Medium- or large-scale preparation methods are required to understand their biological functions and potential applications in life sciences and the biomedical fields. Since ghrelin has an O-acyl modification in its Ser3, recombinant expression for its production has not solely been employed thus far. In this chapter, we provide two distinct protocols for the preparation of human ghrelin: a chemical synthesis method for medium-scale (up to hundreds of milligrams) and a semisynthesis method for large-scale (more than grams) preparation. Established Fmoc chemistry for solid-phase synthesis enables the highly efficient procedure for synthesizing ghrelin in the medium scale. Semisynthesis method, the coupling of chemically synthesized O-acylated ghrelin(1-7) with recombinantly expressed ghrelin(8-28), can be applied for larger scale preparation.