Study on the Properties of Recombinant Prolyl Endopeptidase from Abalone (Haliotis discus hannai) Muscle

In order to study the enzymatic characteristics and structure of prolyl endopeptidase from Haliotis discus hannai (Hdh-PEP), recombinant PEP was cloned and highly expressed in E.coli. Hdh-PEP with molecular weight of 85 kDa was successfully purified and its surface hydrophobicity was greatly affected by pH at low value (pH2～6) and temperature (20～60 ℃). Amino acid sequence homology analysis showed that there were three highly conserved sequences in the catalytic domain of Hdh-PEP: Seq 1: K-D-G-T-K/R-I-P, Seq 2: Y-G-Y-G-G-F and Seq 3: I-R-G-G-E-Y/F. Kinetic study revealed that the K_m and k_cat of Hdh-PEP were 5.32 μmol/L and 15.7 s⁻¹, respectively. Specific inhibitors SUAM-14746 and ZPP of PEP had strong inhibition on Hdh-PEP activity, and serine protease inhibitor (PMSF) also exhibited inhibition. A high specific polyclonal antibody toward Hdh-PEP was prepared which could be applied for the detection of native PEP in abalone muscle. The successful in vitro expression of Hdh-PEP and preparation of a specific polyclonal antibody against Hdh-PEP provided an important reference for subsequent investigation on Hdh-PEP.