Related Experiment Video
Updated: Aug 6, 2026

Specificity Analysis of Protein Lysine Methyltransferases Using SPOT Peptide Arrays
Published on: November 29, 2014
Evidence for overlapping substrate specificity between large neutral amino acid (LNAA) and dipeptide (hPEPT1)
N Surendran1, K M Covitz, H Han
1Department of Pharmacokinetics, Dynamics and Metabolism, Parke-Davis Pharmaceutical Research, Division of Warner-Lambert Company, Ann Arbor, Michigan 48105, USA. narayanan.surendran@wl.com
Purpose:
The objective of this research was to investigate the substrate specificity of large neutral amino acid carrier (LNAA) and di/tripeptide (hPEPT1) transporters with respect to PD 158473, an NMDA antagonist.
Methods:
Cellular uptake studies were carried out using two types of Chinese Hamster Ovary (CHO). CHO-K1 cells represent the wild type with inherent large neutral amino acid (LNAA) activity. CHO-PEPT1 cells were generated by stable transfection of hPEPT1 gene into CHO cells. Therefore, these cells possess both LNAA activity and di/tripeptide transporter activities as a result of the transfection. Cellular uptake of PD 158473 was quantified using a HPLC method previously developed in our laboratory.
Results:
The utility of the CHO-PEPT1 cell model was demonstrated by determining the uptake kinetics of Gly-Sar, a prototypical dipeptide transporter substrate. Uptake kinetics of PD 158473 displayed two carrier-mediated transport components in CHO-PEPT1 cells, while in CHO-K1 cells the relationship was consistent with classic one component Michaelis-Menten kinetics. These results confirmed the affinity of PD 158473 for both LNAA and di/tripeptide transporters. Further, results from inhibition experiments using these two cell types indicate that the high affinity-low capacity system was the LNAA carrier and the low affinity-high capacity carrier was the di/tripeptide transporter.
Conclusions:
This study demonstrates overlapping substrate specificity between LNAA carrier and di/tripeptide transporter (hPEPT1) for PD 158473, an amino acid analog. Establishing Structure Transport Relationship (STR) for this overlap will aid in a design strategy for increasing oral absorption or targeting specific drugs to selected tissues.
More Related Videos
Related Concept Videos
The Significance of Membrane Transport
Transporters facilitate either an active or passive movement of solutes. They can allow a single-molecule transport down its...
Secondary Active Transport
Lysosomal Hydrolases
Pore Transport and Ion-Pair Transport
Pore transport, also known as convective transport, is a process where small molecules like urea, water, and sugars rapidly cross cell membranes as though there were channels or pores in the membrane. Although direct microscopic evidence is limited but the concept of pores or channels is widely accepted based on physiological evidence. Despite the lack of direct microscopic...

