Disorders of Amino Acid Metabolism

Abstract

The chapter discusses the disorders of amino acid metabolism. In reviewing the literature on metabolic disorders of amino acids, one is struck by the abundance of clinical and biochemical data compared with the paucity of morphological observations. Lesions found in these disorders are scanty and largely nonspecific. Therefore, the classification of these diseases is based exclusively on clinical and biochemical criteria. Aminoaciduria, the principal feature of these disorders, is considered as one of the criteria for classification. The study of inborn errors of amino acid transport, carried out by methods of molecular genetics, has revealed that certain genes are responsible for the synthesis of carrier proteins, permeases, and other polypeptides that are essential for the penetration of amino acids through the cell membrane. The tissue specificity of certain aminoacidurias proves that the same amino acid is transported by different mechanisms in different tissues. Almost all disorders of amino acid breakdown are associated with aminoaciduria. In contrast with the transport abnormalities, this malfunction is because of overflow. The disorders of amino acid metabolism can be classified on the basis of their pathophysiological mechanism into overflow, transport, and secondary aminoacidurias.