Novel Helicobacter pylori alpha 1,2-fucosyltransferase, a key enzyme in the synthesis of Lewis antigens

Helicobacter pylori lipopolysaccharides (LPS) contain complex carbohydrates known as Lewis antigens which may contribute to the pathogenesis and adapt ation of the bacterium. Involved in the biosynthesis of Lewis antigens is a n alpha 1,2-fucosyltransferase (FucT) that adds fucose to the terminal beta Gal unit of the O-chain of LPS, Recently, the H, pylori (Hp) alpha 1,2-fuc T-encoding gene (fucT2) was cloned and analysed in detail. However, due to the low level of expression and instability of the protein, its enzymic act ivity was not demonstrated. In this study, the Hp fucT2 gene was successful ly overexpressed in Escherichia coli, Sufficient amounts of the protein wer e obtained which revealed alpha 1,2-fucosyltransferase activity to be assoc iated with the protein. A series of substrates were chosen to examine the a cceptor specificity of Hp alpha 1,2-fucT, and the enzyme reaction products were identified by capillary electrophoresis. In contrast to the normal mam malian alpha 1,2-FucT (H or Se enzyme), Hp alpha 1,2-FucT prefers to use Le wis X [beta Gal1-4(alpha Fuc1-3)beta GlcNAc] rather than LacNAc [beta Gal1- 4 beta GlcNAc] as a substrate, suggesting that H, pylori uses a novel pathw ay (via Lewis X) to synthesize Lewis Y. Hp alpha 1,2-FucT also acts on type 1 acceptor [beta Gal1-3 beta GlcNAc] and Lewis a [beta Gal1-3(alpha Fuc1-4 )beta GlcNAc], which provides H, pylori with the potential to synthesize H type 1 and Lewis b epitopes. The ability to transfer fucose to a monofucosy lated substrate (Lewis X or Lewis a) makes Hp alpha 1,2-FucT distinct from normal mammalian alpha 1,2-FucT.