Purification and identification immunomodulatory peptide from rice protein hydrolysates

ABSTRACT To prepare immunomodulation peptides from rice protein hydrolysates (RPHs), trypsin was employed for enzymatic hydrolysis, and the immunomodulating activities of RPHs were studied using mouse peritoneal macrophage proliferation assay. The peptide fractions with the highest activity were further purified using macroporous adsorption resin, strong cation-exchange chromatography, gel filtration chromatography and reversed-phase high-performance liquid chromatography. The peptide sequence was identified as Tyr-Gly-Ile-Tyr-Pro-Arg (YGIYPR) by high-performance liquid chromatography electrospray ionization quadrupole time-of-flight mass spectrometer. Evaluating its immunomodulatory activity showed that YGIYPR enhanced the proliferation of macrophage RAW 264.7 cells in the range of 12.5–100 μg/mL, and even a minimum dose achieved good proliferation. The results demonstrated that the RPHs prepared by trypsin could serve as a source of immunomodulating peptides and the immunomodulatory peptide YGIYPR is a potential natural ingredient for manufacture of functional foods or health care products. Abbreviations: RP-HPLC: Reversed-phase high-performance liquid chromatography; HPLC-ESI-Q-TOF MS: High-performance liquid chromatography electrospray ionization quadrupole time-of-flight mass spectrometer; YGIYPR: Tyr-Gly-Ile-Tyr-Pro-Arg; RP: Rice protein: RPHs: Rice protein hydrolysates; MAR: Macroporous adsorption resins; TFA: Trifluoroacetic acid; MW: Molecular weight; SI: Stimulation index; DMSO: Dimethyl sulfoxide; MTT: 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide