GALNS and mucopolysaccharidosis type 4A: Likewise, Tomatsu et al. attached six glutamic acids to the N-terminus of human N-acetylgalactosamine-6-sulfate sulfatase (GALNS; EC 3.1.6.4) and examined the effects of this artificial GALNS (E6-GALNS) in a mouse model of MPS IVA.