Characteristics of tripeptide transport in human jejunal brush-border membrane vesicles

Biochim Biophys Acta. 1989 Nov 17;986(1):123-9. doi: 10.1016/0005-2736(89)90280-0.


These studies are aimed at characterizing the transport of the tripeptide, glycylglycyl-L-proline (GlyGlyPro) across human jejunal brush-border membrane vesicles. GlyGlyPro (0.65 mM) was hydrolyzed by brush-border membrane vesicles with the extent of hydrolysis per mg protein being 23% at 0.5 min, 57% at 1 min and complete hydrolysis at 60 min. Treatment of the membrane vesicles with gel-complexed papain (to remove membrane peptidases) resulted in minimal hydrolysis of GlyGlyPro up to 10 min of incubation. Measurement of GlyGlyPro influx with papain-treated vesicles in the presence of increasing medium osmolarity showed that uptake occurred into an osmotically reactive intravesicular space. Transport of GlyGlyPro with normal and papain-treated membrane vesicles was similar in the presence of an inward Na+ or K+ gradient. No overshoot phenomenon was observed in the presence of an inward proton gradient (extravesicular pH 5.5; intravesicular pH 7.5). An interior negative membrane potential induced by a K+ diffusion potential in the presence of valinomycin stimulated the uptake of the peptide. The effect of increasing concentrations on initial rates of GlyGlyPro uptake revealed the presence of a saturable component as well as a diffusional component. Preloading the membrane vesicles with 20 mM glycylsarcosylsarcosine stimulated uptake by 4-fold. Uptake of GlyGlyPro was inhibited greater than 50% by dipeptides and tripeptides and less than 15% by free amino acids. These results indicate that GlyGlyPro uptake in jejunal brush-border membrane vesicles is not energized by a Na+ or proton gradient and that transport occurs by carrier-mediated and diffusional processes.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Amino Acids / pharmacology
  • Biological Transport / drug effects
  • Dipeptides / pharmacology
  • Humans
  • Jejunum / metabolism*
  • Kinetics
  • Liposomes
  • Membrane Lipids / metabolism
  • Microvilli / drug effects
  • Microvilli / metabolism*
  • Molecular Sequence Data
  • Oligopeptides / metabolism*
  • Oligopeptides / pharmacology
  • Papain


  • Amino Acids
  • Dipeptides
  • Liposomes
  • Membrane Lipids
  • Oligopeptides
  • glycyl-glycyl-proline
  • Papain