title: Enzymatic hydrolysis optimization of Paphia undulata and lymphocyte proliferation activity of the isolated peptide fractions.
abstract: BACKGROUND
  The immune system is important in preventing and controlling various infectious diseases. Immunoactive peptides derived from food proteins could exert immunomodulatory activity without side effects. Paphia undulata with high-protein is suitable for the production of immunoactive peptides. The objective of this study was to optimize the hydrolysis parameters to maximize the immune activity of hydrolysates from Paphia undulata.
  
  
  RESULTS
  Hydrolysis parameters, including temperature, time and the ratio of alkaline protease to Paphia undulata meat (E/S), were optimized by response surface methodology with a central composite design. The optimum conditions were obtained as follows: temperature, 51 °C; time, 3.14 h; E/S, 4,321 U g(-1) (Paphia undulata meat). Furthermore, hydrolysates obtained under the optimum conditions were fractionated by ultrafiltration and gel filtration on a Sephadex G-25 column. After two-step isolation, the isolated fractions (P2 and P3) including the peptides Pro-His-Thr-Cys, Val-Gly-Try-Thr, Glu-Phe, Leu-Phe, and Glu-Gly-Ala-Lys, Trp-Ile or Trp-Leu, respectively, could significantly enhance lymphocyte proliferation ability.
  
  
  CONCLUSIONS
  These results showed that response surface methodology and two-step separation were efficient for recovery of low-molecular-weight peptides with high spleen lymphocyte proliferation activity, and the isolated fractions of Paphia undulata hydrolysates are potential ingredients for development of functional foods.
authors.affiliation: College of Food Science and Technology, Guangdong Ocean University, Zhanjiang, Guangdong Province, 524088, China.
authors.forename: Xiao Qing
authors.initials: XQ
authors.lastname: He
authors.forename: Wen Hong
authors.initials: WH
authors.lastname: Cao
authors.forename: Guang Kun
authors.initials: GK
authors.lastname: Pan
authors.forename: Liu
authors.initials: L
authors.lastname: Yang
authors.forename: Chao Hua
authors.initials: CH
authors.lastname: Zhang
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D049872:Bivalvia / Q000737:chemistry*; D004044:Dietary Proteins / Q000378:metabolism / Q000494:pharmacology*; D055951:Functional Food; D006868:Hydrolysis; D007109:Immunity / Q000187:drug effects*; D008214:Lymphocytes / Q000378:metabolism*; D008297:Male; D051379:Mice; D010446:Peptide Fragments / Q000378:metabolism / Q000494:pharmacology*; D011492:Protein Hydrolysates / Q000378:metabolism / Q000494:pharmacology*; D017747:Seafood
chemical_list: D004044:Dietary Proteins; D010446:Peptide Fragments; D011492:Protein Hydrolysates
keywords: Paphia undulata; amino acid sequence; gel filtration; lymphocyte proliferation activity; response surface methodology; ultrafiltration