Acid-Vesicle Function, Intracellular Pathogens, and the Action of Chloroquine against Plasmodium falciparum

When lysosomes were first characterized biochemically by de Duve and his colleagues,¹ the low optimal pH of their degradative enzymes suggested that their internal environment was acidic. Because material taken up by phagocytosis was known to enter an acidic intracellular compartment,² de Duve and Wattiaux hypothesized that degradative enzymes (acid hydrolases), their substrates, and an acid pH might combine in that compartment (the secondary lysosome) to provide an appropriate environment for the degradation of internalized macromolecules.³ Subsequently, it became apparent that these vesicles were part of a network that was responsible for the intracellular movement of macromolecules and membranes and…