Abstract: In order to investigate the thermal stability, pH stability and digestion characteristics of paramyosin (PM) in simulated gastrointestinal fluids, we purified PM to homogeneity from the muscle of Perna viridis by consecutive ammonium sulfate fractionation and hydroxyapatite chromatography, and we further identified it by peptide mass fingerprinting (PMF). Circular dichroism (CD) spectroscopy was employed to measure its secondary structure and thermal denaturation temperature. SDS-PAGE was carried out to explore its thermal stability, pH stability and digestion characteristics in simulated gastrointestinal fluids. PM showed a single band corresponding to 99.5 kDa on SDS-PAGE. Using peptide mass fingerprinting, a total of 26 peptide fragments, including 330 amino acid residues, were obtained from purified PM, which revealed 100% identity to PM from Mytilus galloprovincialis, indicating that the purified protein is PM. CD spectral analysis demonstrated that PM had a typical α-helix structure with thermal denaturation temperature (Td) of (56.3 ± 0.2) ℃. No obvious precipitate was observed when PM was heated in the temperature range from 30 to 100 ℃ for 30 min. PM was stable between pH 6.0–11.0. However, it was unstable below pH 5.0 and aggregated. PM could only be partially hydrolyzed by pepsin, trypsin or chymotrypsin individually, while it was effectively degraded by continuous hydrolysis with the three proteinases. However, protein bands with molecular mass of approximately 30 kDa remained undigested. In conclusion, PM from Perna viridis is thermally stable and resistant to gastrointestinal digestion. This work provides a valuable theoretical basis for mussel processing and further study on PM.

Key words: paramyosin, Perna viridis, purification, stability, simulated gastrointestinal digestion