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Cell Wall, Membrane, and Intracellular Peptidase Activities of Propionibacterium shermanii

Department of Dairy and Food Industries, Agricultural University of Norway, PO Box 36, 1432 Ås-NLH, Norway

¹ Corresponding author.

ABSTRACT

A procedure has been developed for the production of spheroplasts from Propionibacterium shermanii and P. shermanii ATCC 9614. Thus, it was also possible to produce clean cell wall, membrane, and intracellular fractions. The solubilized cell wall preparation was nearly free from intracellular markers; leakage of aldolase and malate dehydrogenase was below .5% after 90 min in lysozyme. The purity and homogeneity of the membrane fraction were visualized with electron micrographs. Polyacrylamide gel electrophoresis and a zymogram technique were used to compare peptidases in the pure fractions. Fifteen dipeptides and 2 tripeptides were used as substrates. Peptidases of P. shermanii and P. shermanii ATCC 9614 were found in the solubilized cell wall (one band and one band), membrane (three bands and two bands), and intracellular fractions (six bands and seven bands). The solubilized cell wall fractions from P. shermanii and P. shermanii ATCC 9614 contain peptidases with reflectance values of 0 and 57, respectively. The reflectance 57 peptidase has a broad substrate specificity, that of the reflectance 0 peptidase is slightly narrower. Among the five membrane peptidases two appear to be unique for membranes, those with reflectance values of 28 and 75.

An intracellular peptidases of broad specificity with reflectance value of 55 is found in both strains. The enzymes hydrolyzed most of the 15 dipeptides and the P. shermanii ATCC enzyme hydrolyzed the 2 tripeptides. The reflectance 24/25 intracellular peptidase of the two strains has the same, limited substrate specificity. The intracellular peptidases for each strain hydrolyzed all the dipeptides used and L-leucine-L-leucine-L-leucine, plus L-alanine-L-leucine-glycine for that from P. shermanii ATCC 9614.

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