초록
<P/><P>The β-galactosidases from <I>Lactobacillus reuteri</I> L103 (<I>Lreu</I>βgal), <I>Lactobacillus delbrueckii</I> subsp. <I>bulgaricus</I> DSM 20081 (<I>Lbul</I>βgal), and <I>Bifidobacterium breve</I> DSM 20281 (<I>Bbre</I>βgal-I and <I>Bbre</I>βgal-II) were investigated in detail with respect to their propensity to transfer galactosyl moieties onto lactose, its hydrolysis products <SMALL>D</SMALL>-glucose and <SMALL>D</SMALL>-galactose, and certain sugar acceptors such as <I>N</I>-acetyl-<SMALL>D</SMALL>-glucosamine (GlcNAc), <I>N</I>-acetyl-<SMALL>D</SMALL>-galactosamine (GalNAc), and <SMALL>L</SMALL>-fucose (Fuc) under defined, initial velocity conditions. The rate constants or partitioning ratios (<I>k</I><SUB>Nu</SUB>/<I>k</I><SUB>water</SUB>) determined for these different acceptors (termed nucleophiles, Nu) were used as a measure for the ability of a certain substance to act as a galactosyl acceptor of these β-galactosidases. When using <I>Lbul</I>βgal or <I>Bbre</I>βgal-II, the galactosyl transfer to GlcNAc was 6 and 10 times higher than that to lactose, respectively. With lactose and GlcNAc used in equimolar substrate concentrations, <I>Lbul</I>βgal and <I>Bbre</I>βgal-II catalyzed the formation of <I>N</I>-acetyl-allolactosamine with the highest yields of 41 and 24%, respectively, as calculated from the initial GlcNAc concentration.</P>