New Software for the Identification and Characterization of Peptides Generated during Fontina Ch

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J.Chem.Chem.Eng.6(2012)323-326 New Software for the Identification and Characterization of Peptides Generated during Fontina Cheese Ripening Using Mass Spectrometry Data 

Sabina Valentini ,Massimo Natale 一,Elisa Ficarra and Andrea Barmaz 1.InstitutAgricole mgional,R g.La Roch&e 1/.4.Aosta 11100,Italy 2.BioDigitalValleyS.r1.,via Carlo Viola 78,PontSaintMartin Dj 11026,Italy 3.Department ofControl and Computer Engineering,Politecnico di Torino,Torino 11 029,Italy 

Received:January 12,2012/Accepted:February 21,2012/Published:April 25,2012 Abstract:The aim of this work was to design and implement a new bioinformatics software which is able to identify the protein peptides from the peaks which arise from in-source or MS/MS fragmentation.The oligopeptide fraction was extracted from Fontina cheese at difierent ages of ripening and subsequently analyzed by LC/MS/MS.On the resulting totaIion chromatograms,the peptides were identified by a method based both on the in-source fragmentation detectable with a single-quadrupole mass analyzer and by a new software which was developed.This software performs an in-silico digestion of the major milk proteins,it calculates all the possible peptide fragments which are generated by tl1e loss of the first N-or C-terminal amino acids,and finally,it matches the experimental ion chromatogram with the in-silico which generated theoretical spectrum to identify the exact amino・acid protein sequence of the unknown oligopeptide.With this too1.the useful insights into the proteolytic processes which occur during Fontina cheese aging are obtained.which leads to a beaer knowledge about the functional features of the proteolysis end product. 

Key words:Fontina PDO,cheese ripening,LC-MS/MS,new bioinformatics software 

1.Introduction Cheese maturation involves complex biochemical reactions,in which proteolysis is regarded as being the most important for many varieties.Proteolysis contributes to textural changes(breaking down the as l, as2,D and para—K casein network),it decreases the water activity through water binding by setting free carboxyl and amino groups,and it increases the pH by producing NH3 from deamination of free amino acids. Moreover,proteolysis directly contributes to flavor (release of peptides and amino acids)and off-flavours (biter hydrophobic peptides), also liberating substrates for others reactions.Thus for the 

Corresponding author:Sabina Valentini,Ph.D.,research fields:biochemistry and proteomics in food.E・mail: 

s.valentini@iaraosta.it. 

development of an acceptable cheese favor,a well—balanced breakdown of the protein(i.e.,casein) into small peptides and amino acids is necessary[1】. The progress of proteolysis in many ripened cheese is first catalyzed by residual coagulant(chymosin which has an hydrophilic character has more affinity for the whey fraction,but it can also be partially trapped in the caseins network)and,to a lesser extent, by plasmin and milk proteinases,which results in the formation of large and intermediate—sized peptides which are subsequently degraded by the coagulant and enzymes from starter and non starter microflora of the cheese.which results in the production of small peptides and free amino acids[2].Although a number of microbial enzymes are common to many cheese varieties,the final peptide composition of a cheese reflects its characteristic ripening process.The peptide 324 New Software for the Identification and Characterization of Peptides Generated during Fontina Cheese Ripening Using Mass Spectrometry Data 

profile composition differs according to different stages of ageing,type of manufacturing and territory, which results in the flavour and texture characteristic ofthe particular variety【3]. An effective way which acquires more information on the proteolytic process in cheese is to identify the peptides which produced throughout ripening[4】. Some proteolytic peptides have been identified in exploratory studies which mainly use amino acid sequencing and mass spectrometry, but little information is available on the peptide profile of Fontina cheese,which is an Italian semi—hard and semi—cooked cheese,which is marked with the quality P.D.0.1abel,typically produced in Aosta Valley,made from raw cow milk and ripened for at least 3 months in natural caves. Nowadays various software available online allows users to identify proteins but all of them are focused on human or human model proteins data sets. Furthermore,the peptides data-base which is used for molecular weight matching is generated by in-silico digestion with only few proteolytic enzymes. The aim of this work was to design and implement the new bioinformatics software which is able to identify the protein peptides from the peaks arising from in—source or MS/MS fragmentation.