Genetic Characterization and Gene Expression of Bile Salt Hydrolase (bsh ) from Lactobacillus Reuteri Crl 1098,a Probiotic Strain

BUSTOS, ANA YANINA; FONT DE VALDEZ, GRACIELA; RAYA, RAUL; TARANTO, MARIA PIA

International Journal of Genomics, Proteomics, Metabolomics & Bioinformatics (IJGPMB)

SciDoc Publishers

Año: 2016 vol. 1 p. 1 - 8

2332-2756

Intestinal microbes containing the bile salt hydrolase (BSH) enzyme, releases free BA plus aminoacids from conjugated BA.BSH activity triggerscholesterol consumption in liver to synthesize BA de novo leading to consequential cholesterol lowering.Lactobacillus(L.)reuteriCRL 1098 is a probiotic bacterium with a proven hypocholesterolemic effect associated to its ability tohydrolyze BA. In this work we characterized the bile salt hydrolase (bsh)operonof CRL 1098 strain as a single open readingframe of 978 nucleotides that encodesa predicted protein of 325 amino acids, with a calculated mass of 36098.1 Daand a theoretical pI of 4.81. Moreover, deduced BSH protein had high similarity with BSHs of other L. reuteri strain andalso exhibited similarity to the Pencillin V amidases of Listeria and Bacillus strains. Five catalytically important amino acidswere highly conserved in Lactobacillus, Enterococcus and Bifido bacterium strains while four amino acid motifs aroundthese active sites, were only partially conserved. After the bsh gene product was expressed in the heterologous host LactococcuslactisNZ9000.The activity was specific towards bile acids but not against alternative substrates. Finally, a significant upregulationof the bsh gene was observed at pH 5.2 (optimal pH of BSH activity).Our studies suggest that BSHs would have an important but so far unknown role in the physiology and lifestyle of L. reuteristrains. The present work would be useful to unravel the ecological role of the BSH and to deepen their influence in thereduction of blood cholesterol levels.