Candida albicansexo-b-1,3-glucanase (Exg; EC ) is implicated in cell wall b-d-glucan remodelling through its glucosyl hydrolase and⁄or transglucosylase activities. A pair of antiparallel phenylalanyl residues (F144 and F258) flank the entrance to the active site pocket. Various Exg mutants were studied using steady-state kinetics and crystallography aiming to understand the roles played by these residues in positioning the b-1,3-d-glucan substrate.