Direct Evidence for Peptide Transporter (PepT1)-Mediated Uptake of a Nonpeptide Prodrug, Valacyclovir

• Published in: Biochemical and biophysical research communications Vol. 250; no. 2; pp. 246 - 251
• Main Authors: Balimane, Praveen V., Tamai, Ikumi, Guo, Ailan, Nakanishi, Takeo, Kitada, Hideyuki, Leibach, Frederick H., Tsuji, Akira, Sinko, Patrick J.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 18.09.1998
• Subjects: Acyclovir - analogs & derivatives; Acyclovir - metabolism; Animals; Biological Transport; Carrier Proteins - genetics; Carrier Proteins - metabolism; Female; Gene Expression; Humans; Oocytes; Peptide Transporter 1; Prodrugs - metabolism; RNA, Complementary - genetics; Symporters; Valine - analogs & derivatives; Valine - metabolism; Xenopus laevis
• ISSN: 0006-291X; 1090-2104
• DOI: 10.1006/bbrc.1998.9298

Xenopus laevisoocytes were used as a gene expression system to characterize the carrier-mediated transport of valacyclovir (vacv), the L-valine ester prodrug of the acyclic nucleoside acyclovir (acv). A significant increase in the uptake of [3H]vacv byXenopus laevisoocytes injected with human intestinal peptide transporter (hPepT1) cRNA compared to the uptake by water injected oocytes indicated that vacv was translocated by hPepT1. Vacv uptake was found to be concentration dependent, saturable (Km= 5.94 ± 1.91mM and Jmax= 1.68 ± 0.25 nmoles/hr/oocyte), pH dependent, and inhibited by various known substrates of hPepT1 but not by acv, valine or pentaglycine. Vacv also inhibited the uptake of14C-glycylsarcosine, a known substrate of hPepT1, in a concentration-dependent manner (Ki= 4.08 ± 1.02mM). These results demonstrate that human intestinal peptide transporter hPepT1 has broad specificity since it recognizes vacv as a substrate even though it lacks a typical peptide bond.