Research article - Peer-reviewed, 2008
Identification of peptides in milk as a result of proteolysis at different levels of somatic cell counts using LC MALDI MS/MS detection
Wedholm, Anna; Moller, Hanne S.; Lindmark-Mansson, Helena; Rasmussen, Morten D.; Andren, Anders; Larsen, Lotte B.Abstract
The somatic cell count (SCC) in milk is associated with increasing proteolytic degradation of caseins and it has been suggested that enzymes derived from somatic cells contribute to a lower yield and poorer quality of cheese. It is essential to increase the knowledge on naturally occurring milk proteinase activities to better understand how to improve the technological quality of milk. The aim of this work was to identify peptides actually present in milk as a result of proteolysis at different levels of SCC and to assign these peptides to potential responsible proteases where possible. Peptide fractions were prepared from acid whey by ultrafiltration at a molecular cut-off value of 10 000 Da. The peptides were separated using capillary reversed phase high performance liquid chromatography (RP-HPLC) and identified by matrix-assisted laser desorption/ionization-time of flight tandem mass spectrometry (MALDI-TOF MS/MS). Peptides identified ranged in mass from 1023 to 2000 Da, and originated from alpha(S1)-, alpha(S2)- or beta-casein. Possible responsible proteases that could be suggested when examining the peptide cleavage sites included plasmin, cathepsin B, D and leukocyte elastase. The results indicated that plasmin was primarily responsible for the observed proteolysis in milk at low cell count, whereas the cathepsins and elastase became implicated at elevated cell count. Specificity and activity of cathepsins and elastase has earlier mainly been studied in model systems, whereas less is known about their activities in milk itself. This is also the first indication of involvement of elastase in milk proteolysis through the unequivocal determination of cleavage sites.Keywords
casein; cathepsin; elastase; plasminPublished in
Journal of Dairy Research2008, volume: 75, number: 1, pages: 76-83
Publisher: CAMBRIDGE UNIV PRESS
Authors' information
Wedholm, Anna
Swedish University of Agricultural Sciences, Department of Food Science
Møller, Hanne S.
Danish Institute of Agricultural Sciences
Lindmark-Månsson, Helena
Swedish Dairy Association
Rasmussen, Morton D.
Danish Institute of Agricultural Sciences
Andrén, Anders
Swedish University of Agricultural Sciences, Department of Food Science
Larsen, Lotte B.
Danish Institute of Agricultural Sciences
UKÄ Subject classification
Food Science
Veterinary Science
Animal and Dairy Science
Publication Identifiers
DOI: https://doi.org/10.1017/S0022029907002968
URI (permanent link to this page)
https://res.slu.se/id/publ/20659