Tracing the pattern of casein breakdown by Lactobacillus delbrueckii subsp. lactis CRL 581.

HÉBERT, E.M,; G. MAMONE,; G. PICARIELLO; M. PESCUMA; S. FADDA; G. SAVOY,; P. FERRANTI

Buenos Aires, Argentina

Congreso; LAHUPO 1st Annual Iberoamerican Proteomics Congress; 2007

LA HUPO

Lactobacillus delbrueckii subsp. lactis is a lactic acid bacterium (LAB) used as starter culture for the manufacture of a variety of fermented dairy products. For growth in milk LAB depend on the presence of a complete proteolytic system which allows the efficient degradation and utilization of casein, the major milk protein. The specialized proteolytic system consists of a cell envelope-associated proteinase (CEP), transport systems, and several intracellular peptidases. The hydrolysis of casein is initiated by a CEP, being the main enzyme of this system. In addition to the vital role for bacterial growth, LAB proteolytic system also contributes to the development of flavor and texture of fermented products. Furthermore, certain LAB strains can release bioactive health-beneficial peptides from casein during milk fermentation. L. delbrueckii subsp. lactis CRL 581, a natural isolate bacterium from Argentinian hard cheese, produces a cell envelope-associated proteinase (PrtL) which hydrolyzed as- and b-casein. The aim of this work was to carry out a structural analysis of the peptides generated by the L. delbrueckii subsp. lactis CRL 581 proteinase PrtL from a- and b- casein. L. delbrueckii subsp. lactis CRL 581 was grown in a chemically defined medium. PrtL activity of whole cell suspensions was measured by using the chromogenic substrate succinyl-alanyl-alanyl-prolyl-phenylalanine-p-nitroanilide and by SDS-PAGE using as substrate a- and b-casein. The peptides released from a- and b-casein were isolated by reversed-phase HPLC and their amino acid compositions were analyzed by mass spectrometry. Twenty- and twenty four-peptides were identified from a- and b-casein hydrolysates, respectively. By characterizing the peptide sequence, the pattern of a- and b-casein breakdown was defined. This pattern would allow predicting the release of bioactive peptides such as antihypertensive, antimutagenic or antimicrobial which are hidden in the inactive state in the original protein sequence.