Interaction of 31 β-lactam antibiotics with the H +/peptide symporter PEPT2: analysis of affinity constants and comparison with PEPT1

The activity of the renal peptide transporters PEPT2 and PEPT1 determines—among other factors such as metabolic stability in liver and plasma—the circulatory half-life of penicillins and cephalosporins during therapy. This study was initiated to examine systematically the interaction of β-lactam antibiotics with PEPT2. Interaction of 31 cephalosporins and penicillins with the carrier protein was characterized by measuring their ability to inhibit the uptake of [ 14C]Gly-Sar into renal SKPT cells. Cefadroxil, cefaclor, cyclacillin, cephradine, cephalexin and moxalactam were recognized by PEPT2 with very high affinity comparable to that of natural dipeptides ( K i=3–100 μM). Ceftibuten, dicloxacillin, amoxicillin, metampicillin, cloxacillin, ampicillin, cefixime, cefamandole, oxacillin and cefmetazole interacted with PEPT2 with medium affinity ( K i=0.1–5 mM). For the other β-lactam antibiotics studied interaction was very low or not measurable ( K i>5 mM). The affinity constants of β-lactam antibiotics at rPEPT2 and hPEPT1 are significantly correlated, but the rank orders are not identical. Decisive differences between PEPT1 and PEPT2 recognition of the N-terminal part of the compounds became evident. Moreover, this large data set of affinity constants of β-lactam antibiotics will be useful for structure–transport (binding) analyses of PEPT2.