p-Dimethylsulfoniophenol (DSP) ester was applied on the reconstruction of peptide, because its hydrophilicity was favorable for the reaction performed in aqueous media. As an example, the biological response of an enzymatically digested peptide hormone, Substance P(SP), was recovered by the reaction with pyroglutamyl (pGlu)-Phe-DSP. This result showed that pGlu-Phe-DSP restored the active site of SP destroyed by the enzyme.