Gene Expression and Specific Activity of the Bile Salt Hydrolase of Lactobacillus reuteri CRL 1098

BUSTOS, ANA YANINA; FONT DE VALDEZ, G; RAYA, R; TARANTO, M. P.

Puerto Madryn

Congreso; XLVI Reunión Anual de SAIB; 2010

Bile acids (BA) act as biological detergent to emulsy and solubilize dietary lipids, facilitating their intestinal absorption. Lactobacillus (L.) reuteri CRL1098, a probiotic strain that showed to be effective in preventing hypercholesterolemia in mice, encodes a bile salt hydrolase (BSH) able to deconjugate the amino acid moiety from the conjugated BA. BSH belongs to the category of enzymes that act on carbon-nitrogen bonds other than peptide bonds in linear amides; other members of this enzyme category include the penicillin and cephalosporin acylases. In this work, the regulation of the CRL 1098 hsb gene and the specific activity of its HSB enzyme, against BA and alternative substrates, were studied. Real Time-PCR reactions showed no differences in the levels of bsh-mRNA transcripts, both in cells grew in the absence or in the presence of 1 mM conjugated BA (TDCA or GDCA), as well as in cells grew in MRS broth at different controlled pH values (4.5, 5.2 and 6.5). Cell free extracts of a Lactococcus lactis NZ9000 recombinant strain carrying the CRL1098 bsh gene showed hidrolizing activity towards all BA assayed, but not against penicillin V, ampicillin, ketocaproylhomoserine lactone, and oxoctanoyl-homoserine lactone. These results suggest that BSH of Lactobacillus reuteri CRL 1098 is a constitutive enzyme and confirm its specificity against BA substrates.