Amino acids, peptides, and proteins

Background Amino acids are the building blocks of proteins, but they also play diverse roles in the provision of energy and the formation of a number of other important biomolecules, including hormones, neurotransmitters, and signaling molecules. The polymers of amino acids, peptides, and proteins orchestrate and control the vast array of human physiologic and biochemical processes. The catalog of amino acids, peptides, and proteins in various biological fluids is a target-rich environment for the detection of pathological states. Content This chapter first describes the chemistry, metabolism, transport, and analysis of amino acids. Polymers of amino acids may be relatively short (peptides) or long (proteins). The human genome contains the information to dictate formation of approximately 20, 000 polypeptides, but the actual diversity of the human proteome and peptidome is manifold more expansive. Proteome diversity arises from linear amino acid sequence and an array of modifications that include acylation, phosphorylation, glycosylation, and isoprenylation. Systems of short peptides, larger protein monomers, and multimeric protein complexes are the tools that orchestrate and control human physiologic and biochemical processes. Proper synthesis, folding, subcellular targeting, and catabolism of proteins and peptides, therefore, are essential for human health. Analytic exploitation of biologic fluids including blood, urine, and cerebrospinal fluid using chemical, immunologic, and mass spectrometric methods enables informed diagnosis and therapy in a multitude of disease states.