Role of dipeptidyl peptidase IV in uptake of peptide nitrogen from beta-casomorphin in rabbit renal BBMV

Abstract

We examined the handling of radiolabeled beta-casomorphin, Tyr-Pro-[3H]Phe-Pro-Gly, by rabbit renal brush-border membrane vesicles (BBMV). The uptake of radiolabel into the vesicles was Na+-independent, but an inward-directed H+ gradient stimulated the uptake. The H+ gradient-dependent uptake was further accelerated by an interior-negative membrane potential, but inhibited in the presence of a protonophore. Treatment of the membrane vesicles with diisopropylfluorophosphate (DFP) greatly reduced the uptake of the radiolabel. Control as well as DFP-treated vesicles exhibited H+ gradient-dependent Gly-Sar uptake. Unlabeled beta-casomorphin inhibited Gly-Sar uptake in control vesicles, but the inhibition was significantly reduced in DFP-treated vesicles. DFP inhibited the activity of dipeptidyl peptidase IV in these vesicles and there was a direct correlation between the activity of the enzyme and the capacity of beta-casomorphin to inhibit Gly-Sar uptake. Many di- and tripeptides reduced the uptake of Gly-Sar and the uptake of radiolabel from beta-[3H]casomorphin to a similar extent. We conclude that beta-casomorphin is hydrolyzed by dipeptidyl peptidase IV and the products are transported into the vesicles by the H+ gradient-driven peptide transport system. This conclusion is supported by the results from the analysis of the incubation medium by high-performance liquid chromatography that showed rapid hydrolysis of the pentapeptide by brush-border membranes to di- and tripeptides.

Decisive structural determinants for the interaction of proline derivatives with the intestinal H+/peptide symporter

“…The role of proline in dipeptides in their transport by peptide carriers has not been studied systematically. Reviewing the available data reveals that at least some Xaa‐Pro dipeptides are good substrates for both renal and intestinal type peptide transporters [12–15]. There is almost no information available regarding the effect of N‐terminal proline on the interaction of dipeptides with PEPT1.…”

“…Using brush‐border membrane vesicles from rabbit kidney, Miyamoto et al . [12] and Daniel et al . [14] found very low or undetectable affinities of Pro‐Gly and Pro‐Leu to the renal peptide transporter(s).…”

“…There is almost no information available regarding the effect of N-terminal proline on the interaction of dipeptides with PEPT1. Using brush-border membrane vesicles from rabbit kidney, Miyamoto et al [12] and Daniel et al [14] found very low or undetectable affinities of Pro-Gly and Pro-Leu to the renal peptide transporter(s). Similarly, in Caco-2 cells, an excess of Pro-Gly (.…”

Absorption of intact β-casomorphins (β-CM) in rabbit ileum in vitro

“…4). This system represents a barrier for natural (Hartrodt et al, 1982;Kreil et al, 1983;Miyamoto et al, 1987). DPP IV is known to be located in the brush-border membrane (Auricchio et al, 1978).…”

Inhibition of dipeptidyl aminopeptidase IV (DP-IV) by Xaa-boroPro dipeptides and use of these inhibitors to examine the role of DP-IV in T-cell function.

“…In mammalian systems, a number of different biological functions for DP-IV have been proposed, ranging from digestion (15) and amino acid salvage (16), because of its occurrence in the intestine and kidney, to an involvement, through proteolytic processing, in fibronectin-mediated cell movement and adhesion (17). Because of the high frequency of Gly-Pro sequences in collagen, Hopsu-Havu et al (18) suggested that this enzyme may play a role in collagen metabolism or catabolism.…”