A molecular insight into the proteolytic system of Lactobacillus delbrueckii subsp. lactis

HEBERT, E.M.

Mesa redonda; SIBAL 2016. V International Symposium on Lactic Acid Bacteria. Benefitting from Lactic Acid Bacteria. Progress in Health and Food.; 2016

A molecularinsight into the proteolytic system of Lactobacillusdelbrueckii subsp. lactisElvira M.HebertCentro de Referencia para Lactobacilos (CERELA-CONICET) - Chacabuco 145? CP-4000 S. M. de Tucumán. ehebert@cerela.org.ar The proteolytic system of Lactobacillus has an essential role in bacterial growth,contributes to the flavor development of fermented products, and can releasebioactive health-beneficial peptides during milk fermentation. Lactobacillus delbrueckii ssp. lactis CRL 581, a thermophilic lactic acid bacterium used asa starter culture for the manufacture of several fermented dairy products,possesses an efficient proteolytic system that is able to release a series ofpotentially bioactive peptides (i.e., antihypertensive, anti-inflammatory andphosphopeptides) from α- and β-caseins. A genomicanalysis of the proteolytic system of L.delbrueckii subsp. lactis CRL 581reveals genes encoding the cell envelope-associated proteinase (prtL),peptide transport systems (oppand opt) and sixteen peptidases. It was observedthat the production of bioactive peptides by the proteinase (PrtL) wasrepressed 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 PrtLactivity was inhibited 99-, 70-, and 68-fold, respectively. Then, the influence of the peptide supply ontranscription of 23 genes involved in the proteolytic system of L. delbrueckii subsp. lactis was examined after cell growth ina chemically defined medium (CDM) and CDM plus Casitone by qRT-PCR analysis.While prtL, oppA1, optS, optA as well as oppDFBC and optBCDF operonswere the most highly expressed genes in CDM,their expression were repressed 6- to 115-fold by the addition of Casitone. Theproteomic approach confirmed transcriptional analysis; an up-regulation ofPrtL, PepG, OppD and OptF was observed. Contrariwise, a DNA-binding protein(YebC) was up-regulated by Casitone. Binding of YebC to prtL promoter region demonstrated that YebC acts as a transcriptionalrepressor. This is the firstreport that correlates transcriptional and proteomic analysis of theproteolytic system of L. delbrueckiiand demonstrates that YebC modulates the proteinase biosynthesis