Human BACE polypeptides having modifications to the N-linked glycosylation
sites including one or more of the following amino acid substitutions:
S174I, N223A, N153Q and N354S. DNA sequences, vectors, and host cells for
producing the polypeptides. Crystalline protein compositions formed from
the purified polypeptides. Methods of screening for compounds that
inhibit A.beta. using the polypeptides.