The sequence variant c.215A>T in exon 2 changes histidine in position 72 to leucine(p.His72Leu). Studies in transfected cells show that p.Leu72 is inactive, but processed correctly and localized to the lysosomes. p.His72 is located in the active site where it is directly involved in coordination of the cofactor Zn²⁺, and 3d-modelling indicates that the substitution changes the metal binding site and thus the catalytic properties of the enzyme. Hence, p.His72Leu is an active site mutant.