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Applied and Environmental Microbiology, June 2008, p. 3682-3689, Vol. 74, No. 12
0099-2240/08/$08.00+0 doi:10.1128/AEM.00247-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.
Characterization of the Pattern of 
s1- and β-Casein Breakdown and Release of a Bioactive Peptide by a Cell Envelope Proteinase from Lactobacillus delbrueckii subsp. lactis CRL 581
Elvira María Hebert,1*
Gianfranco Mamone,2
Gianluca Picariello,2
Raúl R. Raya,1
Graciela Savoy,1
Pasquale Ferranti,3 and
Francesco Addeo3
Centro de Referencia para Lactobacilos (CERELA-CONICET), 4000 San Miguel de Tucumán, Argentina,1 Centro di Spettrometria di Massa Proteomica e Biomolecolare, ISA-CNR, Via Roma 52A-C, 83100 Avellino, Italy,2 Dipartimento di Scienza degli Alimenti, University of Naples Federico II, Parco Gussone, 80055 Portici, Italy3
Received 28 January 2008/ Accepted 10 April 2008
The cell envelope-associated proteinases (CEPs) of the lactobacilli have key roles in bacterial nutrition and contribute to the development of the organoleptic properties of fermented milk products as well, as they can release bioactive health-beneficial peptides from milk proteins. The influence of the peptide supply, carbohydrate source, and osmolites on the CEP activity of the cheese starter Lactobacillus delbrueckii subsp. lactis CRL 581 was investigated. The CEP activity levels were controlled by the peptide content of the growth medium. The maximum activity was observed in a basal minimal defined medium, whereas in the presence of Casitone, Casamino Acids, or yeast extract, the synthesis of CEP was inhibited 99-, 70-, and 68-fold, respectively. The addition of specific di- or tripeptides containing branched-chain amino acids, such as leucylleucine, prolylleucine, leucylglycylglycine, or leucylproline, to the growth medium negatively affected CEP activity, whereas dipeptides without branched-chain amino acids had no effect on the enzyme's production. The carbon source and osmolites did not affect CEP activity. The CEP of L. delbrueckii subsp. lactis CRL 581 exhibited a mixed-type CEPI/III variant caseinolytic specificity. Mass-spectrometric screening of the main peptide peaks isolated by reverse-phase high-pressure liquid chromatography allowed the identification of 33 and 32 peptides in the 
s1- and β-casein hydrolysates, respectively. By characterizing the peptide sequence in these hydrolysates, a pattern of s1- and β-casein breakdown was defined and is reported herein, this being the first report for a CEP of L. delbrueckii subsp. lactis. In this pattern, a series of potentially bioactive peptides (antihypertensive and phosphopeptides) which are encrypted within the precursor protein could be visualized.
* Corresponding author. Mailing address: CERELA-CONICET, Chacabuco 145, 4000 San Miguel de Tucumán, Argentina. Phone: 54-3814310465. Fax: 54-3814005600. E-mail: ehebert{at}cerela.org.ar
Published ahead of print on 18 April 2008.
Applied and Environmental Microbiology, June 2008, p. 3682-3689, Vol. 74, No. 12
0099-2240/08/$08.00+0 doi:10.1128/AEM.00247-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.
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