Cloning and expression of a bile salts hydrolase gene from Lactobacillus reuteri CRL 1098

BUSTOS AY, FONT DE VALDEZ G, RAYA R, TARANTO MP

Villa Carlos Paz, Córdoba, Argentina

Congreso; SAIB 2008; 2008

SAIB

Bile acids (BA) are biological detergents that play an essential role in fat digestion. Theyare synthesized from cholesterol in the liver and then released into the intestines, wheremay be extensively modified by the indigenous intestinal bacteria. Microbial bile salthydrolase (BSH) is an important enzyme that hydrolizes the amide bond of theglycine/taurine moiety of BA from the steroid core. A close relationship has beendemonstrated between BSH and the ability of Lactobacillus (L.) reuteri CRL 1098 toremove cholesterol in vitro. In this work, the hsb gene from the sourdough isolate L. reuteriCRL 1098 was amplified by PCR techniques. The deduced sequence was shown to have99% similarity with a choloylglycine hydrolase from L. reuteri F275. The hsb gene with itsputative promotor region was cloned and expressed in Escherichia coli DH 10b andLactococcus lactis NZ9000. L. lactis NZ9000 (BSH+) cell free extracts (CFE) showedBSH activity towards all BA assayed (5 mM of GDCA, TDCA, GCA or TCA). For someBA, the BSH values were similar or even higher than those detected in the wild-type L.reuteri CRL 1098. In particular, higher values were observed towards GDCA in bothsstrains. These results confirmed the functionality of the hsb gene of L. reuteri CRL 1098and will contribute to the knowledge of BA metabolism in probiotic microorganisms.