Plasmepsin-2 is a malarial aspartic proteinase that has been implicated in the initial steps of hemoglobin degradation in parasites and thus represents an attractive antimalarial. target. Escherichia coli expressed proplasmepsin-2 is capable of activation at acidic pH by autocatalytic cleavage of the pro part region, which results in products of different length. We designed a 10-amino-acid deletion in the pro part region that allows faster generation of homogeneous enzyme upon activation. Incorporation of a (HiS)(6) tag onto the N-terminus of the pro part enables on-column refolding of proplasmepsin-2 and simplifies proenzyme purification and pro part separation after activation. The proposed purification procedure results in highly pure and easily crystallizable enzyme. (C) 2002 Elsevier Science (USA).