Plays a role in the catabolism of L-fucose, a sugar that is part of the carbohydrates that are attached to cellular glycoproteins. Catalyzes the dehydration of L-fuconate to 2-keto-3-deoxy-L-fuconate by the abstraction of the 2-proton to generate an enediolate intermediate that is stabilized by the magnesium ion. May down-regulate thymidylate synthase activity, possibly already at the RNA level, by promoting the degradation of TYMS mRNA via an antisense RNA-based mechanism. L-fuconate = 2-dehydro-3-deoxy-L-fuconate + H2O Binds 1 Mg(2+) ion per subunit. Could be sumoylated. Belongs to the mandelate racemase/muconate lactonizing enzyme family. ENOSF1 subfamily.