초록
<B>Abstract</B>Background<P>l-Fucose is a rare sugar with potential uses in the pharmaceutical, cosmetic, and food industries. The enzymatic approach usingl-fucose isomerase, which interconvertsl-fucose andl-fuculose, can be an efficient way of producingl-fucose for industrial applications. Here, we performed biochemical and structural analyses ofl-fucose isomerase identified from a novel species of<I>Raoultella</I>(<I>Rd</I>FucI).</P>Results<P><I>Rd</I>FucI exhibited higher enzymatic activity forl-fuculose than forl-fucose, and the rate for the reverse reaction of convertingl-fuculose tol-fucose was higher than that for the forward reaction of convertingl-fucose tol-fuculose. In the equilibrium mixture, a much higher proportion ofl-fucose (~ ninefold) was achieved at 30 °C and pH 7, indicating that the enzyme-catalyzed reaction favors the formation ofl-fucose froml-fuculose. When biochemical analysis was conducted usingl-fuculose as the substrate, the optimal conditions for<I>Rd</I>FucI activity were determined to be 40 °C and pH 10. However, the equilibrium composition was not affected by reaction temperature in the range of 30 to 50 °C. Furthermore,<I>Rd</I>FucI was found to be a metalloenzyme requiring Mn<SUP>2+</SUP>as a cofactor. The comparative crystal structural analysis of<I>Rd</I>FucI revealed the distinct conformation of α7-α8 loop of<I>Rd</I>FucI. The loop is present at the entry of the substrate binding pocket and may affect the catalytic activity.</P>Conclusions<P><I>Rd</I>FucI-catalyzed isomerization favored the reaction froml-fuculose tol-fucose. The biochemical and structural data of<I>Rd</I>FucI will be helpful for the better understanding of the molecular mechanism ofl-FucIs and the industrial production ofl-fucose.</P>