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 (Ki=3-100 μM). Ceftibuten, dicloxacillin, amoxicillin, metampicillin, cloxacillin, ampicillin, cefixime, cefamandole, oxacillin and cefmetazole interacted with PEPT2 with medium affinity (Ki=0.1-5 mM). For the other β-lactam antibiotics studied interaction was very low or not measurable (Ki>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.