Proton/peptide cotransporter (PEPT 2) from human kidney: functional characterization and chromosomal localization

Area of Science:

• Molecular Biology
• Human Physiology
• Genetics

Background:

• The human kidney plays a crucial role in reabsorbing peptides and amino acids.
• Understanding peptide transporters is vital for drug delivery and metabolic studies.
• PEPT 2 is a known peptide transporter, but its detailed functional characteristics and gene localization require further elucidation.

Purpose of the Study:

• To functionally characterize the H+/peptide cotransporter PEPT 2 cloned from human kidney.
• To determine the chromosomal localization of the PEPT 2 gene.
• To compare the substrate affinity of PEPT 2 with the human intestinal transporter PEPT 1.

Main Methods:

• Functional expression of PEPT 2 in HeLa cells.
• Transport assays using the neutral dipeptide glycylsarcosine.
• Kinetic analysis (Michaelis-Menten kinetics) to determine transporter affinity.
• Somatic cell hybrid analysis and in situ hybridization for gene mapping.

Main Results:

• PEPT 2 functionally expressed in HeLa cells mediates glycylsarcosine transport.
• Transport activity is pH-dependent, with an optimum between pH 6.0 and 7.0.
• PEPT 2 exhibits high affinity for glycylsarcosine (Km = 74 ± 14 μM), significantly higher than PEPT 1.
• PEPT 2 demonstrates broader substrate specificity and higher affinity for various dipeptides compared to PEPT 1.
• The gene encoding PEPT 2 was mapped to human chromosome 3q13.3-q21.

Conclusions:

• PEPT 2 is a high-affinity, pH-sensitive peptide transporter in the human kidney.
• PEPT 2 has a distinct substrate specificity and higher affinity than PEPT 1.
• The localization of the PEPT 2 gene to chromosome 3 provides a genetic marker for further studies.