Mechanisms of peptide transport.

This review touches on the development of the concept of transmembrane transport of peptides, which originated more than 100 years ago, and discusses present knowledge of the phenomenon, with special reference to intestinal absorption of peptides. It deals with (1) Peptide transport in animal small intestine and its main features--active transport of di- and tripeptides into the absorptive cells, the question of sodium or proton dependence of peptide transport, the independence of peptide and amino acid transport, competition for transport between peptides, the number of transport systems involved, the influence of molecular structure on peptide transport, transport kinetics and relative rates of absorption of peptides and amino acids, nutritional and therapeutic aspects of peptide transport, mechanisms of absorption of small peptides of dietary origin and mechanisms of absorption of biologically active peptides (2) Peptide transport in other animal cells and tissues (3) Peptide transport in microorganisms (4) Peptide transport in higher plants and (5) Physiological advantages of peptide transport. The concluding remarks stress that though most of the salient features of peptide absorption may have been established by 1975, more investigators might usefully be engaged in studying the many remaining questions concerning peptide transport in the animal body, and point out the unfortunate effects of too narrow an approach to problems in the field.