Sodium-dependent neutral amino acid transport by human liver plasma membrane vesicles

Mark E. Mailliard, Michael S. Kilberg

Research output: Contribution to journalArticlepeer-review

30 Scopus citations


The activities of several selected Na+-dependent amino acid transporters were identified in human liver plasma membrane vesicles by testing for Na+-dependent uptake of several naturally occurring neutral amino acids or their analogs. Alanine, 2-(methylamino)isobutyric acid, and 2-aminoisobutyric acid were shown to be almost exclusively transported by the same carrier, system A. Kinetic analysis of 2-(methylamino)isobutyric acid uptake by the human hepatic system A transporter revealed an apparent Km of 0.15 mM and a Vmax of 540 pmol·mg-1 protein·min-1. Human hepatic system A accepts a broad range of neutral amino acids including cysteine, glutamine, and histidine, which have been shown in other species to be transported mainly by disparate carriers. Inhibition analysis of Na+-dependent cysteine transport revealed that the portion of uptake not mediated by system A included at least two saturable carriers, system ASC and one other that has yet to be characterized. Most of the glutamine and histidine uptake was Na+-dependent and the component not mediated by system A constituted system N. The largest portion of glycine transport was mediated through system A and the remainder by system ASC with no evidence for system Gly activity. Our examination of Na+-dependent amino acid transport documents the presence of several transport systems analogous to those described previously but with some notable differences in their functional activity. Most importantly, the results demonstrate that liver plasma membrane vesicles are a valuable resource for transport analysis of human tissue.

Original languageEnglish (US)
Pages (from-to)14321-14326
Number of pages6
JournalJournal of Biological Chemistry
Issue number24
StatePublished - Aug 25 1990
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


Dive into the research topics of 'Sodium-dependent neutral amino acid transport by human liver plasma membrane vesicles'. Together they form a unique fingerprint.

Cite this