Transmembrane Transport of Small Peptides

Abstract

Publisher Summary This chapter deals with the transmembrane transport of small peptides in animals, in microorganisms, and in higher plants. Active transmembrane transport of small peptides is a mechanism of very wide distribution in nature and is of major biological importance. The main characteristics of peptide transport in animal intestine, the scutellum of germinating barley, a yeast, and in Escherichia coli (E. coli), are summarized in a tabulated form. The chapter discusses the intralumen and brush border hydrolysis of proteins and peptides , the active uptake of small peptides by the absorptive cells, the effects of peptides on intestinal transport of Na + and water, competition for mucosal uptake among peptides, and the kinetics of intestinal absorption of peptides. The general features of nutritional utilization of peptides by microorganisms, the nature of the microbial cell surface and membrane location of peptide permeases, the methods for studying peptide transport, and the peptide transport in bacteria and other microorganisms are also presented in the chapter. Various possible physiological advantages of transmembrane transport of small peptides are reviewed. Peptide uptake, as opposed to the uptake of free amino acids, might reduce the energy requirement for the transport in more than one way. One of these ways is that if peptides entering the cell are rapidly hydrolyzed, the peptide concentration within the cell may be maintained at a lower level than that outside it. In such a case, peptides could enter the cell by a process of facilitated diffusion, no expenditure of metabolic energy being required.