Amino Acids

Like all other organisms, parasitic protozoa and helminths require the basic set of 20 amino acids for their protein synthesis, formation of other biomolecules, and, to a lesser extent, for energy production. The majority of these amino acids are essential for the parasite and have to be obtained from the diet or from exogenous proteins. Ingested proteins are hydrolyzed within specialized organelles (lysosomes, lysosome-like organelles, and other specialized vacuoles) into their constituent amino acids by the concerted action of specific proteinases and peptidases. In nematodes and trematodes, protein digestion is accomplished in the gut lumen. The amino acid metabolism of parasites resembles that of higher animals, but there are differences regarding the properties of the enzymes involved, the relative importance of the various pathways, and the occurrence of a variety of unusual metabolic routes. The unique properties of amino acid metabolism found in protozoan parasites are often...