Multiple forms of bile salt hydrolase from Lactobacillus sp. strain 100-100

Four isozymes of bile salt hydrolase (BSH) have been purified from the cytosol of cells of Lactobacillus sp. strain 100-100. The four proteins were designated BSH A, B, C, and D. They eluted from anion-exchange high-pressure liquid chromatography columns at 0.15, 0.18, 0.21, and 0.25 M NaCl, respectively. They are catalytically similar, except that the Vmax of BSH D is about 10-fold lower than those of the other three isozymes. All four proteins consist of one or two polypeptides. The peptides have molecular weights of 42,000 and 38,000 and are designated alpha and beta, respectively. The approximate native molecular weights of BSH A, B, C, and D are 115,000, 105,000, 95,000, and 80,000, respectively. The native proteins are probably trimers; the four isozymes are the array of possible subunit combinations alpha 3, alpha 2 beta 1, alpha 1 beta 2, and beta 3 for A, B, C, and D, respectively. The two subunits are antigenically distinct. Polyclonal antibodies raised against BSH A (all alpha peptide) react in Western blots (immunoblots) only with proteins containing the alpha peptide; such antibodies raised against BSH D (all beta peptide) react only with proteins containing the beta peptide. The amino acid compositions of the two peptides differ. This is the first report of a bacterium that makes four BSH isozymes.