Plasmodial hemoglobin degradation: an ordered pathway in a specialized organelle.

During its intraerythrocytic development, the malarial parasite devours most of the hemoglobin in its host cell. This enormous catabolic process is achieved through an ordered, efficient degradative pathway that takes place in a specialized organelle, the digestive vacuole. The amino acids generated are used by the parasite for its growth and maturation; the heme released is polymerized into a crystalline matrix called hemozoin. We are beginning to understand the special enzymes that participate in this pathway. We do not yet fully understand the relative importance of exogenous versus catabolically generated amino acids, the function of hemozoin, the mechanism of action of quinoline drugs that concentrate in the digestive vacuole, or the mechanism of protection from malaria of variant hemoglobin gene carriers.