Proteolytic systems of dairy lactic acid bacteria

Mulholland, Francis

doi:10.1007/978-1-4613-1121-8_9

Cited by 2 publications

(1 citation statement)

References 84 publications

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“…Additionally, proteolytic enzymes from LAB produce flavor compounds and precursors that are essential for cheese flavor development (Mulholland 1997; Chen and Steele 1998). The proteolytic systems of LAB can be functionally divided into three components: (1) cell envelope‐associated proteinases, which hydrolyze caseins to oligopeptides; (2) peptide transport systems, of which the oligopeptide transport system is the most important in milk and cheese; and (3) numerous intracellular peptidases (Kunji et al.…”

Section: Introductionmentioning

confidence: 99%

Hydrolysis of Major Dairy Proteins by Lactic Acid Bacteria From Bulgarian Yogurts

Tzvetkova

Dalgalarrondo

Danova

et al. 2007

J Food Biochemistry

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Twenty‐one Lactobacillus strains isolated from three types of Balkan homemade yogurts were grown on sodium caseinate, β‐casein or whey proteins, and the proteolysis was followed by electrophoresis and reversed‐phase high‐performance liquid chromatography. The best conditions allowing obtaining proteolysis without casein precipitation are 0.8% casein in 50‐mM phosphate buffer. The strains tested showed a relatively high proteolytic activity despite the limited conditions for bacterial growth. Within 72 and 96 h of incubation, 80–90% of β‐casein was consumed. They showed also a proteolytic activity toward α‐lactalbumin (ALA), being able to reduce its concentration between 5 and 55%, depending on the strains used. The capacity of the strains to hydrolyze β‐lactoglobulin was lower as compared with hydrolysis of ALA. Hydrolysis of casein by all strains produced peptides with an antibacterial effect against Escherichia coli. Consequently, to obtain a maximal hydrolysis of the dairy proteins seconded by appearance of antimicrobial peptides, a combination of strains with different beneficial properties to be used as starters was proposed. PRACTICAL APPLICATIONS Some of the 21 Lactobacillus strains isolated from three types of Balkan homemade yogurts may be used to proteolyze milk proteins in order to produce peptides with an antibacterial effect against Escherichia coli. To obtain a maximal hydrolysis of the dairy proteins seconded by appearance of antimicrobial peptides, a combination of strains with different beneficial properties to be used as starters should be determined. During fermentation process, milk proteins are acidified by the production of lactic acid and are hydrolyzed by proteases and peptidases from bacteria. This proteolysis is followed by a reduction of the number of epitopes and consequently by a decrease in allergenicity of hydrolyzed proteins. For these reasons, starters as Lactobacillus strains with beneficial properties able to reduce the allergenicity of fermented milk products are of great interest for the dairy industry.

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Section: Introductionmentioning

confidence: 99%

Hydrolysis of Major Dairy Proteins by Lactic Acid Bacteria From Bulgarian Yogurts

Tzvetkova

Dalgalarrondo

Danova

et al. 2007

J Food Biochemistry

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Identification and Characterization of Lactobacillus helveticus PepO2, an Endopeptidase with Post-Proline Specificity

Chen¹,

Christensen

Broadbent

et al. 2003

Appl Environ Microbiol

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A post-proline endopeptidase (PepO2) was detected in cell extracts from a genomic library of Lactobacillus helveticus CNRZ32 by using the synthetic substrate N-acetyl-␤-casein-(f203-209)--nitroanilide in a coupled reaction with aminopeptidase N. Isolates with activity for this substrate contained plasmids with visually indistinguishable restriction profiles. Nucleotide sequence analysis revealed a 1,947-bp open reading frame, designated pepO2, encoding a putative 71.4-kDa protein. Analysis of the predicted peptide sequence revealed that L. helveticus PepO2 contained the zinc-dependent metalloprotease motif HEXXH and exhibited levels of amino acid sequence similarity of 72, 61, 59, and 53% to L. helveticus PepO, Lactococcus lactis PepO2, L. lactis PepO, and Lactobacillus rhamnosus PepO, respectively. Northern hybridization results indicated that the transcript containing pepO2 was monocistronic. Despite the high degrees of amino acid similarity to PepO proteins from other lactic acid bacteria, the specificity of the L. helveticus PepO2 for post-proline bonds distinguishes it from other PepO-type endopeptidases characterized to date. The specificity for post-proline bonds also suggests that this enzyme may play a central role in the hydrolysis of casein-derived bitter peptides, such as ␤-casein(f193-209).The proteolytic systems of dairy lactic acid bacteria (LAB) have received extensive research attention due to their importance in the physiology of these organisms and in cheese flavor development. LAB are fastidious microorganisms with multiple amino acid auxotrophies (18). During growth in milk, LAB rely on their proteolytic systems to obtain essential amino acids from caseins (CNs), the most abundant proteins in milk (9, 17). Additionally, proteolytic enzymes from LAB produce flavor compounds and precursors that are essential for cheese flavor development (9, 23).The proteolytic systems of LAB can be functionally divided into three components: (i) cell envelope-associated proteinases which hydrolyze CNs to oligopeptides; (ii) peptide transport systems, of which the oligopeptide transport system is the most important in milk and cheese; and (iii) numerous intracellular peptidases (9, 17). The intracellular peptidases of LAB include both endopeptidases and aminopeptidases. Endopeptidases, due to their ability to hydrolyze peptide bonds within a peptide, are of particular interest in targeting peptides for rapid hydrolysis. In Lactococcus lactis, the best-characterized LAB, the endopeptidases that have been identified include PepO, PepO2, PepF1, and PepF2. All of these enzymes are metalloproteases, and PepO, PepF1, and PepF2 are encoded in operons (9, 17). The physiological roles of these endopeptidases remain unclear; however, PepF appears to be important for protein turnover during nitrogen starvation (24). To date, one metalloendopeptidase, designated PepO (8), and a thiol-dependent endopeptidase, designated PepE (13), have been characterized from Lactobacillus helveticus.The ability of L. helveticus CNRZ32 to ...

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Proteolytic systems of dairy lactic acid bacteria

Cited by 2 publications

References 84 publications

Hydrolysis of Major Dairy Proteins by Lactic Acid Bacteria From Bulgarian Yogurts

Hydrolysis of Major Dairy Proteins by Lactic Acid Bacteria From Bulgarian Yogurts

Identification and Characterization of Lactobacillus helveticus PepO2, an Endopeptidase with Post-Proline Specificity

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