請用此 Handle URI 來引用此文件: http://hdl.handle.net/11455/69883
標題: In situ generation of milk protein-derived peptides in drying-off cows
作者: Ho, C.H.
Chang, C.J.
Liu, W.B.
Peh, H.C.
Chen, S.E.E.
Chen, H.Y.
Ho, T.H.
Chen, M.T.
Nagahata, H.
關鍵字: Bioactive peptides
MALDI-TOF MS
LC-ESI MS/MS
mammary secretion
dry
cows
tight junction integrity
mammary-gland
physicochemical properties
bioactive peptides
gelatinase-b
cathepsin-b
casein
purification
proteolysis
identification
期刊/報告no:: Journal of Dairy Research, Volume 77, Issue 4, Page(s) 487-497.
摘要: Our previous studies demonstrated prompt elevation of proteinase activity in mammary secretion of drying-off cows and goats. The current study examined the progressive changes in composition of cow mammary secretion following drying-off and, in parallel, characterized the mode of peptide neogenesis using matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF MS) and liquid chromatography-electrospray-ionization (LC-ESI) MS/MS. The results show that the percentage of casein of total milk protein at time of drying-off was 76%, which dropped to 41%, 24%, and 16%, respectively, 1, 2, and 3 weeks after drying-off. Levels of beta-lactoglobulin and alpha-lactoalbumin in mammary secretions of drying-off cows decreased prominently while levels of lactoferrin, BSA, and casein derived-proteins increased concomitantly compared with regular milk. A fractionation procedure was applied to remove molecules larger than 10 kDa before MALDI-TOF MS and LC-ESI MS/MS and the results show that the MALDI-TOF MS peptide profile of mammary secretion ranging from m/z 600 to 4000 was apparently modified after drying-off for 1 week, whereas species 1590 m/z and 2460 m/z were most obviously enriched compared with regular milk. LC-ESI MS/MS results were used to map peptide sequence with Mascot search server and under no post translational modification to reduce database size and 202 novel beta-casein-derived peptides were successfully identified in mammary secretion after drying-off for 1 week in contrast to regular milk. Accordingly at least 48 additional cleavage positions were assigned on beta-casein for mammary secretion. Among the 202 novel peptides, 5 are homologous with confirmed opioid agonists, angiotensin 1-converting enzyme inhibitors, or immuno-moclulators. In conclusion, peptides are released in situ from milk proteins within short intervals following drying-off in cows, They might play roles in the transition of mammary glands from lactating to non-lactating. With specified post-translational modifications and focused functional screening, novel peptides are yet to be discovered in dry cow mammary secretion.
URI: http://hdl.handle.net/11455/69883
ISSN: 0022-0299
文章連結: http://dx.doi.org/10.1017/s0022029910000634
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