5 - Amino Acid and Protein Metabolism

Abstract

This chapter explains the metabolism of amino acid and protein. Many parasites can utilize amino acids as energy sources during their life cycle and most amino acids can be used by at least one group of parasites. The chapter focuses on recent findings and pathways that appear to be especially active in parasites or have unique features, which distinguish the parasite's metabolism.The ways in which parasite and host amino acid metabolism differ include the extent of alanine formation in many protozoan parasites and aspects of sulfur amino acid metabolism in anaerobic protozoa and helminths. Protein degradation provides a source of amino acids for many parasites. Many of the proteolytic enzymes likely to be involved are well characterized and the roles played by some of these in specific proteolytic processes are being identified. In many respects the basic features of amino acid and protein metabolism of parasitic protozoa and helminths resemble those of their mammalian hosts. Proteins are broken down extracellularly or within lysosomes, and amino acids taken up and used for biosynthesis or energy metabolism. The chapter summarizes that although, many of the features of parasite amino acid and protein metabolism resemble those of the hosts, there are marked differences with respect to the properties of the enzymes involved, the relative importance of common pathways and the presence of parasite-specific pathways.