title: Variability of hydrolysis of β-, αs1-, and αs2-caseins by 10 strains of Streptococcus thermophilus and resulting bioactive peptides.
abstract: Milk proteins contain numerous potential bioactive peptides, which may be released by digestive proteases or by the proteolytic system of lactic acid bacteria during food processing. The capacity of  Streptococcus thermophilus  to generate peptides, especially bioactive peptides, from bovine caseins was investigated. Strains expressing various levels of the cell envelope proteinase, PrtS, were incubated with α(s1)-, α(s2)-, or β-casein. Analysis of the supernatants by LC-ESI-MS/MS showed that the β-casein was preferentially hydrolyzed, followed by α(s2)-casein and then α(s1)-casein. Numbers and types of peptides released were strain-dependent. Hydrolysis appeared to be linked with the accessibility of different casein regions by protease. Analysis of bonds hydrolyzed in the region 1-23 of α(s1)-casein suggests that PrtS is at least in part responsible for the peptide production. Finally, among the generated peptides, 13 peptides from β-casein, 5 from α(s2)-casein, and 2 from α(s1)-casein have been reported as bioactive, 15 of them being angiotensin-converting enzyme inhibitors.
authors: Unité de Recherche Animal et Fonctionnalités des Produits Animaux (UR AFPA), Équipe Protéolyse et Biofonctionnalités des Protéines et des Peptides (PB2P), Nancy-Université, Vandœuvre-lès-Nancy, France.
authors: Laurent
authors: L
authors: Miclo
authors: Emeline
authors: E
authors: Roux
authors: Magali
authors: M
authors: Genay
authors: Emilie
authors: E
authors: Brusseaux
authors: Chantal
authors: C
authors: Poirson
authors: Nawara
authors: N
authors: Jameh
authors: Clarisse
authors: C
authors: Perrin
authors: Annie
authors: A
authors: Dary
mesh_terms: D000595:Amino Acid Sequence; D000806:Angiotensin-Converting Enzyme Inhibitors / Q000494:pharmacology; D000818:Animals; D001426:Bacterial Proteins / Q000378:metabolism; D002364:Caseins / Q000737:chemistry* / Q000378:metabolism*; D002417:Cattle; D006868:Hydrolysis; D008969:Molecular Sequence Data; D010455:Peptides / Q000032:analysis* / Q000378:metabolism* / Q000494:pharmacology; D012697:Serine Endopeptidases / Q000378:metabolism; D048249:Streptococcus thermophilus / Q000378:metabolism*
chemical_list: D000806:Angiotensin-Converting Enzyme Inhibitors; D001426:Bacterial Proteins; D002364:Caseins; D010455:Peptides; C417204:PrtS protein, Streptococcus thermophilus; D012697:Serine Endopeptidases