Confirming the popular tradition, recent clinical studies have clearly demonstrated that donkey’s milk (DM) may represents a safe and alternative food in both IgE-mediated and non-IgE-mediated cow’s milk protein allergy (CMPA), providing nutritional adequacy and good palatability [ , , ]. Although the mechanism of this tolerance has not yet been fully clarified, it is reasonable to hypothesize that the reduced allergenic properties of DM can be related to structural differences of its protein components with respect to bovine milk. Consequently, DM has recently aroused scientific and clinical interest, above all among pediatric allergologists. Notwithstanding this growing interest and although composition, physico-chemical and nutritional properties of DM are well known, until ten years ago protein characterization of DM at molecular level was still scanty and regarded only the most abundant whey proteins (i.e. α-lactalbumin and β-lactoglobulins). Therefore, with the aim to improve the knowledge about the DM protein composition, in the last years we have undertaken a systematic characterization of the protein profile of different DM samples by mass spectrometry-based approaches coupled with highly efficient separation techniques (i.e. RP-HPLC and 2D-PAGE) and bioinformatic tools. As first result of this investigation the primary structure of a new variant of -lactoglobulin II [ ], of lactoferrin and serum albumin [ ], of two splicing variants of β-casein [ ], four isoforms of αs1-casein [ ] and four isoforms of αs2-casein [ ], were characterized. Phosphorilation level of the two β-casein splicing variants was determined. The informations obtained evidenced remarkable differences in the IgE-binding linear epitopes of cow’s proteins and the corresponding domains present in DM proteins and these differences could be related to the already demonstrated low allergenic properties of donkey’s milk. Recently we expanded the knowledge on “hidden” proteome of DM applying the ProteoMiner technology [ ]. This approach allowed the identification of 106 donkey’s milk unique gene products, a list that appears to be by far the most extensive protein profiling of this milk currently available [ ]. A preliminary evaluation of the qualitative composition of cow and she-donkey milk proteome does not reveal significant differences and, therefore, the lower allergenic properties of DM with respect to cow’s milks seem to be mainly related to the remarkable differences in the primary structure of the major proteins. On the other hand, an investigation of individual milk samples has revealed the existence of individual DM samples lacking single protein components (e.g. β-LG and αs1-CN) [ ]. Thus, determination of the relationship between protein composition and allergenic properties appears of relevant interest. To this aim, alternative methods such as affinity-mass spectrometry :::::: may provide more sensitive and specific tools then immunological procedures. Finally, because the use of DM is in the diet of allergenic children, rapid and accurate methods to detect the presence, even at low concentrations, of bovine or caprine milk in raw DM appear desirable. In this respect, it has been shown that MALDI-TOF MS represents an useful approach to detect bovine or caprine milk contamination of DM at level as low as 2% [ ].
|Titolo:||Mass spectrometry-based proteomics of equidae milk|
|Data di pubblicazione:||2012|
|Appare nelle tipologie:||4.2 Abstract in Atti di convegno|