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Appl. Environ. Microbiol., Sep 1996, 3220-3226, Vol 62, No. 9
M Gobbetti, E Smacchi and A Corsetti
A cell envelope 57-kDa proteinase, a cytoplasmic 65-kDa dipeptidase, and a
75-kDa aminopeptidase were purified from Lactobacillus sanfrancisco CB1
sourdough lactic acid bacterium by sequential fast protein liquid
chromatography steps. All of the enzymes are monomers. The proteinase was
most active at pH 7.0 and 40 degrees C, while aminopeptidase and
dipeptidase had optima at pH 7.5 and 30 to 35 degrees C. Relatively high
activities were observed at the pH and temperature of the sourdough
fermentation. The proteinase is a serine enzyme. Urea-polyacrylamide gel
electrophoresis of digest of alpha s1- and beta-caseins showed differences
in the pattern of peptides released by the purified proteinase and those
produced by crude preparations of the cell envelope proteinases of
Lactobacillus delbrueckii subsp. bulgaricus B397 and Lactococcus lactis
subsp. lactis SK11. Reversed- phase fast protein liquid chromatography of
gliadin digests showed a more-complex peptide pattern produced by the
proteinase of Lactobacillus sanfrancisco CB1. The dipeptidase is a
metalloenzyme with high affinity for dipeptides containing hydrophobic
amino acids but had no activity on tripeptides or larger peptides. The
aminopeptidase was also inhibited by metal-chelating agents, and showed a
broad N-terminal hydrolytic activity including di- and tripeptides. Km
values of 0.70 and 0.44 mM were determined for the dipeptidase on Leu-Leu
and the aminopeptidase on Leu-p-nitroanilide, respectively.
Copyright © 1996, American Society for Microbiology
The proteolytic system of Lactobacillus sanfrancisco CB1: purification and characterization of a proteinase, a dipeptidase, and an aminopeptidase
Institute of Dairy Microbiology, Agricultural Faculty of Perugia, Italy.
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