Abnormalities in the Metabolism of Sulfur-Containing Amino Acids

Abstract

The chapter presents a discussion on the irregularities in the metabolism of sulfur-containing amino acids. The chapter begins by stating that disorders in the metabolism of sulfur-containing amino acids have an honored place in the history of biochemistry and medicine. The latter disease was also one of the biochemical defects upon which Garrod based the concept of the inborn errors of metabolism. The chapter states that biochemistry has profited from the metabolic studies of patients with cystinuria, and cystathioninemia might have remained a clinical enigma had not the biochemists discovered the details of the pathway from methionine to cysteine. The chapter focuses on specific clinical entities, which are now recognized as genetic defects in the metabolism of methionine, homocysteine, and cystathionine. Metabolic transfer across membranes deserves special consideration, and abnormalities in the intestinal and renal transport of methionine and cysteine are discussed in the same context as the more generally accepted inborn errors of metabolism. The chapter also discusses cystinosis, although it is premature to consider it as an established genetic defect of amino acid metabolism.