Cell-wall-associated proteinase of Lactobacillus delbrueckii subsp. bulgaricus CNRZ 397: differential extraction, purification and properties of the enzyme.
Whole cells of Lactobacillus delbrueckii subsp. bulgaricus CNRZ 397 were able to hydrolyse alpha- and beta-caseins. Irrespective of the growth medium used, milk or De Man-Rogosa-Sharpe (MRS) broth, identical patterns of alpha- and beta-casein hydrolytic products, respectively, were visualized by sodium dodecyl sulphate-polyacrylamide gel electrophoresis. A soluble proteinase present in cell-wall extracts was active on caseins and displayed the same hydrolytic patterns as whole cells. It was purified from cell-wall extract to homogeneity by ultrafiltration and ion exchange chromatography. The enzyme is a monomer with a molecular mass of 170 kDa, an optimum temperature of 42 degrees C and an optimum pH of 5.5. It was strongly activated by dithiothreitol and partially inhibited by E-64. These properties indicate that cysteine residues play an important role in the enzyme mechanism. The purified proteinase was not able to hydrolyse di- or tripeptides.
Laboratoire de Microbiologie et Génétique Moléculaire, Université Claude Bernard--Lyon I, Villeurbanne, France.
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Laloi
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Atlan
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Blanc
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Gilbert
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Portalier
D000595:Amino Acid Sequence; D000596:Amino Acids; D001426:Bacterial Proteins / Q000302:isolation & purification* / Q000378:metabolism; D002364:Caseins / Q000378:metabolism; D002473:Cell Wall / Q000201:enzymology*; D002863:Chromogenic Compounds / Q000378:metabolism; D010450:Endopeptidases / Q000302:isolation & purification* / Q000378:metabolism; D006868:Hydrolysis; D007778:Lactobacillus / Q000201:enzymology*; D008969:Molecular Sequence Data; D013379:Substrate Specificity
D000596:Amino Acids; D001426:Bacterial Proteins; D002364:Caseins; D002863:Chromogenic Compounds; D010450:Endopeptidases