Purification and characterization of encystment-induced glucosamine 6-phosphate isomerase in Giardia

Giardia intestinalis encystment results in the incorporation of galactosamine (GalN) (a cyst- wall specific sugar) into outer cyst wall filaments [1,2]. GalN is synthesized during encystment from endogenous glucose by an inducible enzyme pathway [3] and the first reaction unique to GalN synthesis is the conversion of fructose-6-phosphate (F6P) to glucosamine 6-phosphate (G1cN6P) [4,5].