Intestinal uptake of dipeptides and beta-lactam antibiotics. I. The intestinal uptake system for dipeptides and beta-lactam antibiotics is not part of a brush border membrane peptidase

Biochim Biophys Acta. 1990 Nov 30;1030(1):41-9. doi: 10.1016/0005-2736(90)90236-h.

Abstract

The uptake of beta-lactam antibiotics into small intestinal enterocytes occurs by the transport system for small peptides. The role of membrane-bound peptidases in the brush border membrane of enterocytes from rabbit and pig small intestine for the uptake of small peptides and beta-lactam antibiotics was investigated using brush border membrane vesicles. The enzymatic activity of aminopeptidase N was inhibited by beta-lactam antibiotics in a non-competitive manner whereas dipeptidylpeptidase IV was not affected. The peptidase inhibitor bestatin led to a strong competitive inhibition of aminopeptidase N whereas the uptake of cephalexin into brush border membrane vesicles was only slightly inhibited at high bestatin concentrations (greater than 1 mM). Modification of brush border membrane vesicles with the histidine-modifying reagent diethyl pyrocarbonate led to a strong irreversible inhibition of cephalexin uptake whereas the activity of aminopeptidase N remained unchanged. A modification of serine residues with diisopropyl fluorophosphate completely inactivated dipeptidylpeptidase IV whereas the transport activity for cephalexin and the enzymatic activity of aminopeptidase N were not influenced. With polyclonal antibodies raised against aminopeptidase N from pig renal microsomes the aminopeptidase N from solubilized brush border membranes from pig small intestine could be completely precipitated; the binding protein for beta-lactam antibiotics and oligopeptides of apparent Mr 127,000 identified by direct photoaffinity labeling with [3H]benzylpenicillin showed no crossreactivity with the aminopeptidase N anti serum and was not precipitated by the anti serum. These results clearly demonstrate that peptidases of the brush border membrane like aminopeptidase N and dipeptidylpeptidase IV are not directly involved in the intestinal uptake process for small peptides and beta-lactam antibiotics and are not a constituent of this transport system. This suggests that a membrane protein of Mr 127,000 is (a part of) the uptake system for beta-lactam antibiotics and small peptides in the brush border membrane of small intestinal enterocytes.

MeSH terms

  • Affinity Labels
  • Aminopeptidases / antagonists & inhibitors
  • Aminopeptidases / metabolism
  • Animals
  • Anti-Bacterial Agents / metabolism*
  • Anti-Bacterial Agents / pharmacology
  • Binding, Competitive
  • CD13 Antigens
  • Carrier Proteins / analysis
  • Carrier Proteins / metabolism
  • Cephalexin / metabolism
  • Dipeptides / metabolism*
  • Dipeptidyl Peptidase 4
  • Dipeptidyl-Peptidases and Tripeptidyl-Peptidases / antagonists & inhibitors
  • Dipeptidyl-Peptidases and Tripeptidyl-Peptidases / metabolism
  • Endopeptidases / metabolism*
  • Immunosorbent Techniques
  • Intestinal Absorption*
  • Intestine, Small / metabolism
  • Leucine / analogs & derivatives
  • Leucine / pharmacology
  • Microvilli / enzymology*
  • Molecular Weight
  • Penicillin G / metabolism
  • Photochemistry
  • Rabbits
  • Swine

Substances

  • Affinity Labels
  • Anti-Bacterial Agents
  • Carrier Proteins
  • Dipeptides
  • Endopeptidases
  • Aminopeptidases
  • CD13 Antigens
  • Dipeptidyl-Peptidases and Tripeptidyl-Peptidases
  • Dipeptidyl Peptidase 4
  • Leucine
  • ubenimex
  • Cephalexin
  • Penicillin G