Expression of Plm I, II, IV, V, IX, X and HAP occurs in the erythrocytic cycle, and expression of Plm VI, VII, VIII, occurs in the exoerythrocytic cycle.
There are four types of plasmepsins, closely related but varying in the specificity of cleavage site.
Plasmepsins I and II cleave hemoglobin between residues Phenylalanine 33 and Leucine 34 of α-globin subunit.
The name plasmepsin may come from Plasmodium (the organism) and pepsin (a common aspartic acid protease with similar molecular structure).
The closest (non-pathogenic) enzymatic equivalent in humans is the beta-secretase enzyme.