Caracterización genética de la proteinasa de Lactobacillus delbrueckii subsp lactis CRL 581.

ESPECHE TURBAY, B.; SAVOY DE GIORI, G.; HEBERT, E.M.

Cordoba, Argentina

Congreso; III Congreso Internacional de Ciencia y Tecnología de los Alimentos.; 2009

Lactobacillus delbrueckii subsp. lactis is a thermophilic lactic acid bacterium (LAB) used as a starter culture for the manufacture of hard cheeses, such as Grana and Provolone. Growth of LABs in milk mainly depends on the presence of a complete proteolytic system which allows the efficient degradation and utilization of casein, the major milk protein. The cell envelope-associated proteinase (CEP) is the main enzyme of this system which, besides the hydrolysis of casein, contributes to the development of the organoleptic properties of cheeses. In certain LABs, the CEP is able to release bioactive peptides. Previously, we demonstrated that L. delbrueckii subsp lactis  CRL 581 hydrolyzed alpha- and beta-caseins releasing peptides with antihipertensive and antimutagenic activities. In this work, by using degenerate primers based on different LAB CEP DNA sequences, the CEP gene of Lactobacillus delbrueckii subsp. lactis CRL 581 (prtL) was identified, sequenced and characterized. The chromosomally located prtL gene consisted of about 6 Kb; its deduced amino acid sequence would indicate that the proteinase is most probably synthesized as a preprotein of 211 KDa, with an N-terminal signal peptide domain characteristic of exported proteins of gram-positive bacteria. Conserved motifs surrounding the amino acids D30, H94, S425 and N189, amino acids involved in the active site of serine proteases, were found. PrtL differs from the characterized CEPs of several LABs in the positions which possibly modulate the substrate specificity and binding. As our knowledge, PrtL was the first CEP genetically characterized from L. delbrueckii subsp. lactis. Regulation studies of PrtL production by using RT-PCR are in progress.