AJP - Gastrointestinal and Liver Physiology, Vol 248, Issue 6 682-G686, Copyright © 1985 by American Physiological Society
Transport of glycyl-L-proline by mouse intestinal brush-border membrane vesicles
V. M. Rajendran, A. Berteloot and K. Ramaswamy
The characteristics of [14C]glycyl-L-proline transport have been studied
using brush-border membrane vesicles from mouse small intestine in order to
investigate the transport of nonhydrolyzable peptide across the
brush-border membrane. Uptake curves for the peptide did not exhibit
overshoot phenomena and were similar under Na+ or K+ gradient conditions
(extravesicular greater than intravesicular). However, L-proline was
transported by Na+ gradient-dependent system. Analysis of the incubation
medium and the intravesicular contents showed that there was negligible
hydrolysis of the peptide. Transport of glycyl-L-proline was saturable,
conforming to Michaelis-Menten kinetics with a Km of 30.8 +/- 1.9 mM and a
Vmax of 5.96 +/- 0.17 nmol.mg prot-1.0.4 min-1. Uptake of glycyl-L-proline
was not significantly inhibited by free amino acids nor by most of the
peptides containing D amino acids but was strongly inhibited (up to 64%) by
various di- and tripeptides of L amino acids. These results clearly show
that glycyl-L-proline was transported by a Na+-independent,
carrier-mediated process. Our results suggest that the nonhydrolyzable
peptides are transported mostly by carrier-mediated processes in contrast
to hydrolyzable peptides.
