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Appl. Environ. Microbiol., Jul 1995, 2577-2582, Vol 61, No. 7
J Grill, F Schneider, J Crociani and J Ballongue
Bifidobacterium species deconjugate taurocholic, taurodeoxycholic,
taurochenodeoxycholic, glycocholic, glycodeoxycholic, and
glycochenodeoxycholic acids. The enzyme level increases in the growth
phase. No increase in activity is observed for the cytoplasmic enzyme after
addition of conjugated bile acids to a stationary-phase culture. Conjugated
bile salt hydrolase (BSH) was purified from Bifidobacterium longum BB536.
Its apparent molecular mass in denaturing polyacrylamide gel
electrophoresis was ca. 40,000 Da. The intact enzyme had a relative
molecular weight of ca. 250,000 as determined by gel filtration
chromatography, suggesting that the native BSH of B. longum is probably a
hexamer. The purified enzyme is active towards both glycine and taurine
conjugates of cholate, deoxycholate, and chenodeoxycholate. The pH optimum
is in the range of 5.5 to 6.5. A loss of BSH activity is observed after
incubation at temperatures higher than 42(deg)C; at 60(deg)C, 50% of the
BSH activity is lost. The importance of free sulfhydryl groups at the
enzyme active center is suggested. For B. longum BB536, no significant
difference in the initial rate of deconjugation and enzymatic efficiency
appears between bile salts. The enzymatic efficiency is higher for B.
longum BB536 than for other genera. In this paper, a new method which
permits a display of BSH activity directly on polyacrylamide gels is
described; this method confirms the molecular weight obtained for B. longum
BB536 BSH.
Copyright © 1995, American Society for Microbiology
Purification and Characterization of Conjugated Bile Salt Hydrolase from Bifidobacterium longum BB536
Laboratoire de Chimie Biologique I, Institut Henry Tissier, Universite de Nancy I, 54506 Vandoeuvre les Nancy Cedex, France
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