L-serine uptake by human placental microvillous membrane vesicles
Lewis, R.M., Glazier, J., Greenwood, S.L., Bennett, E.J., Godfrey, K.M., Jackson, A.A., Sibley, C.P., Cameron, I.T. and Hanson, M.A. (2007) L-serine uptake by human placental microvillous membrane vesicles. Placenta, 28, (5-6), 445-452. (doi:10.1016/j.placenta.2006.06.014).
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The human fetus requires more glycine than any other amino acid but placental glycine transfer to the fetus is insufficient to meet fetal demand. L-Serine could represent a major metabolic source of glycine for the human fetus but little is known about the kinetics and physiology of L-serine uptake by the human placenta. We have characterised the amino acid transport systems involved in the uptake of L-serine by the microvillous membrane of the human placental syncytiotrophoblast and compared the uptake rates to those of glycine. L-Serine uptake into microvillous membrane (MVM) vesicles was primarily mediated by system A (MeAIB inhibitable) and system L (BCH inhibitable). Further characterisation using specific substrates of LAT1 and LAT2 found the pattern of L-serine uptake was consistent with that expected for uptake mediated by LAT2. Uptakes were performed with tracer levels of (14)C-L-serine, physiological levels of L-serine, or with physiological levels of amino acids. As amino acid concentrations rose, the proportion of uptake by System L decreased while uptake by uncharacterised Na(+)-independent systems increased. Uptake of Lserine into MVM vesicles had a V(max) of 2.1+/-0.4 nmol/mg protein/min, which was significantly higher than for glycine (V(max) 1.0+/-0.2 nmol/mg protein/min). This indicates that MVM vesicles have a higher uptake capacity for L-serine than glycine, despite a greater demand for glycine over serine for fetal protein synthesis. Further studies are now required to define the fate of L-serine taken up by the placenta and its importance for the fetus.
|Keywords:||acid, antigens, health, sodium-calcium exchanger, pregnancy, amino acid transport system a, amino acid transport system y+, glycine, kinetics, origins, cd98 light chains, genetics, biological transport, fetus, disease, female, amino acids, microvilli, serine, placenta, human, amino acid transport system y+l, research, neoplasm proteins, fetal, proteins, protein, physiology, metabolism, amino acid transport systems, humans, membrane|
|Subjects:||R Medicine > RG Gynecology and obstetrics
Q Science > QH Natural history > QH301 Biology
|Divisions:||University Structure - Pre August 2011 > School of Medicine
|Date Deposited:||10 Sep 2008|
|Last Modified:||27 Mar 2014 18:43|
|RDF:||RDF+N-Triples, RDF+N3, RDF+XML, Browse.|
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