| Autor: |
Lowe EK; Fonterra Research Centre, Private Bag 11-029, Palmerston North, New Zealand. edwin.lowe@fonterra.com, Anema SG, Bienvenue A, Boland MJ, Creamer LK, Jiménez-Flores R |
| Jazyk: |
angličtina |
| Zdroj: |
Journal of agricultural and food chemistry [J Agric Food Chem] 2004 Dec 15; Vol. 52 (25), pp. 7669-80. |
| DOI: |
10.1021/jf0491254 |
| Abstrakt: |
Heat treatment of milk causes the heat-denaturable whey proteins to aggregate with kappa-casein (kappa-CN) via thiol-disulfide bond interchange reactions. The particular disulfide bonds that are important in the aggregates are uncertain, although Cys(121) of beta-lactoglobulin (beta-LG) has been implicated. The reaction at 60 degrees C between beta-LG A and an activated kappa-CN formed small disulfide-bonded aggregates. The tryptic peptides from this model system included a peptide with a disulfide bond between a Cys residue in the triple-Cys peptide [beta-LG(102-124)] and kappa-CN Cys(88) and others between kappa-CN Cys(88) or kappa-CN Cys(11) and beta-LG Cys(160). Only the latter two novel disulfide bonds were identified in heated (90 degrees C/20 min) milk. Application of computational search tools, notably MS2Assign and SearchXLinks, to the mass spectrometry (MS) and collision-induced dissociation (CID)-MS data was very valuable for identifying possible disulfide-bonded peptides. In two instances, peptides with measured masses of 4275.07 and 2312.07 were tentatively assigned to beta-LG(102-135):kappa-CN(11-13) and beta-LG A(61-69):kappa-CN(87-97), respectively. However, sequencing using the CID-MS data demonstrated that they were, in fact, beta-LG(1-40) and beta-LG(41-60), respectively. This study supports the notion that reversible intramolecular disulfide-bond interchange precedes the intermolecular interchange reactions. |
| Databáze: |
MEDLINE |
| Externí odkaz: |
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