Characteristics And Bioactivities Of Proline-rich Polypeptides Isolated From Bovine Colostrum

Proline-rich polypeptides (PRPs) are newly discovered bioactive substances widespreadly spreaded in cattle, sheep, human and other mammalian colostrums. It's been reported that they have diverse bioactivities such as immunomodulatory, antioxidative and antiviral properties, resistant to DNA mutations and so on. Besides, they play a great role in prevention and treatment of Alzheimer's disease (AD). Due to their potential bioactivities in the health care field, it has been attracting much interest of medical and nutrition researchers. In our study, we isolated PRPs from bovine colostrum, characterized and identified their chemical properties with some protein analysis methods; identified the their component and peptide sequences, carefully studied their bioactivities towards cultured cells.We tested the amino acid composition of PRPs by amino acid analyzation. PRPs had a quite unusual amino acid composition, with 20% proline ratio and a large proportion of hydrophobic amino acids. We studied the gel electrophoresis result of two milk sources—colostrum and common milk, so same steps were taken to deal with the milks. There were same bands between the two but also differences. Compared with common milk, higher abundance of small molecular weight polypeptides (≤25kD) was observed in colostrum products. All of PRPs peptides were of 25kD or below, and 5~14.4kD peptides were in majority; PRPs'hydrophobic characteristic and purity were indicated on reversed-phase column. The result showed that PRPs peptides with similar hydrophobic, 97.3% bioactive peptides from PRPs were eluted under acetonitrile concentration 37% ~ 45%.With the protein electrophoresis bands as the research object, one dimensional electrophoresis and liquid MS analysis technology (1 DE LC-MS/MS) were used to identify the sequences of PRPs proteins or peptides. Through the mass spectrometry testing, the candidate protein were selected or eliminated, and PRPs components were determined. PRPs were composed of three caseins,β-lactoglobulin, secretoglobin, apolipoprotein and bovine serum albumin fragments. The activity of PRPs might be derived from related caseins.We adopted cultured human cell the embryos lung diploid cell line 2BS for research object. During cells incubation in PRPs medium, we monitored the growth status of the cells, the results were used as indexs for assessing PRPs'biological activity. Test methods and results were as follows: investigated the influence of PRPs on cell growth, and the optimal concentration for PRPs incubation was 1μg/mL; stimulated cells with H2O2 for oxidative stress, the total antioxidant capacity were improved, while PRPs decreased the celluar antioxidative value to the normal level 0.17 FeSO4 mol/g; senescence cells were induced by oxidation with a rise in SA-β-Gal level, while PRPs treated cells reduced SA-β-Gal rate by 56.4%. Studies on cells revealed that PRPs adjusted cell viability, weakened oxidative stress and resisted to cell senescence.