Evidence for a glycyl-proline transport system in ovine enterocyte brush-border membrane vesicles.

A peptide transport system in ovine enterocyte BBMV has been examined with glycyl-L-proline (Gly-Pro) as substrate. Transport is stimulated by an inwardly directed proton gradient (pH1 = 8.4; pH0 = 6.0). Gly-Pro uptake was saturable and conformed to Michaelis-Menten kinetics. Uptake was not affected by the presence of glycine but was inhibited by glycyl-L-phenylalanine (Gly-Phe). This is thought to be the first positive demonstration of the existence of a peptide transporter in the ruminant small intestine.