PROTON PEPTIDE COTRANSPORTER (PEPT-2) FROM HUMAN KIDNEY - FUNCTIONAL-CHARACTERIZATION AND CHROMOSOMAL LOCALIZATION

We report here on the functional characterization of the H+/peptide co transporter PEPT 2 cloned from human kidney and on the chromosomal loc alization of the PEPT 2 gene. PEPT 2, when functionally expressed in H eLa cells, induces the transport of the neutral dipeptide glycylsarcos ine. The induced transport activity is markedly influenced by extracel lular pH. The optimum pH for the transport process is 6.0-7.0. Kinetic analysis has revealed that PEPT 2 is a high-affinity transporter, the Michaelis-Menten constant for glycylsarcosine being 74 +/- 14 mu M. T he human intestinal H+/peptide cotransporter PEPT 1 has 4-fold less af finity for the dipeptide under identical experimental conditions. Stud ies with other chemically diverse dipeptides have established that PEP T 2 possesses higher affinity than PEPT 1 not only for neutral peptide s but also for peptides consisting of anionic and/or cationic amino ac ids. Somatic cell hybrid analysis and in situ hybridization have shown that the gene encoding PEPT 2 maps to human chromosome 3q13.3-q21.