title: Detecting β-Casein Variation in Bovine Milk.
abstract: In bovine species, β-casein (β-CN) is characterized by genetic polymorphism. The two most common protein variants are β-CN A² (the original one) and A¹, differing from A² for one amino acid substitution (Pro67 to His67). Several bioactive peptides affecting milk nutritional properties can originate from β-CN. Among them, β-casomorphin-7 (BCM7) ranging from amino acid 60 to 66 can be released more easily from β-CN variants carrying His67 (A¹ type) instead of Pro67 (A² type). Nowadays, "A2 milk" is produced in different countries claiming its potential benefits in human health. The aim of this study was to further develop and apply an isoelectric focusing electrophoresis (IEF) method to bulk and individual milk samples in order to improve its use for β-CN studies. We succeeded in identifying A2 milk samples correctly and quantifying the percentage of A², A¹, and B variants in bulk samples not derived from A2 milk as well as in individual milk samples. The method allows us to quantify the relative proportion of β-CN variants in whole milk without eliminating whey protein by acid or enzymatic precipitation of caseins. The aim of this study was also to study the different behavior of β-CN and β-lactoglobulin (β-LG) in the presence of trichloroacetic acid (TCA). The higher sensitivity of β-CN to TCA allows quantifying β-CN variants after TCA fixation because β-LG is not visible. Monitoring β-CN variation in cattle breeds is important in order to maintain a certain balance between Pro67 and His67 in dairy products. Overall, the debate between A1 and A2 milk needs further investigation.
authors.affiliation: Unit of Biotechnology, Department of Molecular and Translational Medicine, University of Brescia, Brescia 25123, Italy. annamaria.caroli@unibs.it.
authors.forename: Anna Maria
authors.initials: AM
authors.lastname: Caroli
authors.affiliation: Unit of Biotechnology, Department of Molecular and Translational Medicine, University of Brescia, Brescia 25123, Italy. salvatore.savino@unibs.it.
authors.forename: Salvatore
authors.initials: S
authors.lastname: Savino
authors.affiliation: Unit of Biotechnology, Department of Molecular and Translational Medicine, University of Brescia, Brescia 25123, Italy. omar.bulgari@unibs.it.
authors.forename: Omar
authors.initials: O
authors.lastname: Bulgari
authors.affiliation: Unit of Biotechnology, Department of Molecular and Translational Medicine, University of Brescia, Brescia 25123, Italy. eugenio.monti@unibs.it.
authors.forename: Eugenio
authors.initials: E
authors.lastname: Monti
mesh_terms: D000818:Animals; D001947:Breeding; D002364:Caseins / Q000032:analysis* / Q000235:genetics* / Q000302:isolation & purification; D002417:Cattle; D005260:Female; D014644:Genetic Variation; D007525:Isoelectric Focusing; D007782:Lactoglobulins / Q000032:analysis* / Q000235:genetics / Q000302:isolation & purification; D008892:Milk / Q000737:chemistry*; D014238:Trichloroacetic Acid / Q000737:chemistry
chemical_list: D002364:Caseins; D007782:Lactoglobulins; D014238:Trichloroacetic Acid
keywords: bioactive peptide; bovine milk; isoelectric focusing; β-casein
references.citation: Peptides. 1999;20(8):957-62
references.pmid: 10503774
references.citation: Curr Pharm Des. 2003;9(16):1309-23
references.pmid: 12769739
references.citation: J Dairy Sci. 2004 Jun;87(6):1641-74
references.pmid: 15453478
references.citation: J Anim Breed Genet. 2008 Apr;125(2):119-29
references.pmid: 18363977
references.citation: J Chromatogr A. 2008 Jun 27;1195(1-2):101-6
references.pmid: 18495141
references.citation: J Dairy Sci. 2009 Mar;92(3):1192-202
references.pmid: 19233813
references.citation: J Dairy Sci. 2009 Nov;92(11):5335-52
references.pmid: 19841193
references.citation: Food Chem. 2013 Aug 15;139(1-4):549-52
references.pmid: 23561144
references.citation: Eur J Nutr. 2014 Jun;53(4):1039-49
references.pmid: 24166511
references.citation: Int J Food Sci Nutr. 2014 Sep;65(6):720-7
references.pmid: 24649921
references.citation: Eur J Clin Nutr. 2014 Sep;68(9):994-1000
references.pmid: 24986816
references.citation: Food Chem. 2015 Feb 1;168:70-9
references.pmid: 25172685
references.citation: Nucleic Acids Res. 2015 Jan;43(Database issue):D204-12
references.pmid: 25348405
references.citation: Biochim Biophys Acta. 1983 Mar 30;743(3):303-9
references.pmid: 6830811