Modulation of the Cell-Surface Proteinase Activity of Thermophilic Lactobacilli by the Peptide Supply |
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Authors: | Elvira M Hébert Raul R Raya Graciela Savoy de Giori |
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Institution: | (1) Centro de Referencia para Lactobacilos (CERELA) CONICET, Chacabuco 145, 4000 S.M. de Tucumán, Argentina, AR;(2) Cátedra de Microbiologia Superior, Facultad de Bioquímica, Química y Farmacia, Universidad Nacional de Tucumán, Argentina, AR |
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Abstract: | The proteolytic system of thermophilic lactobacilli is considered important for bacterial nutrition as well as for the formation
of flavor and texture in fermented products. We investigated the influence of peptide content on the cell surface proteinase
and intracellular aminopeptidase activities from seven thermophilic lactobacilli strains. The proteinase activities were remarkably
reduced in cells grown in the peptide-rich medium MRS or in a chemically defined medium supplemented with Casitone compared
with those found in a synthetic medium. The degree of inhibition observed was strain dependent. When proteinase activities
were analyzed by their hydrolytic patterns of α- and β-casein degradation, four types of PIII-caseinolytic cleavage specificity were distinguished. Lactobacillus helveticus strains possessed aminopeptidase activities with broader specificity than those found in L. delbrueckii subsp. lactis strains. However, the aminopeptidase activities were not influenced by the peptide content of the medium.
Received: 1 February 2002 / Accepted: 27 February 2002 |
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