Linked Life Data

8585244

Source:http://linkedlifedata.com/resource/pubmed/id/8585244

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
4
pubmed:dateCreated
1996-3-21
pubmed:abstractText
We have determined the kinetic characteristics of alanine transport into brush border membrane vesicles (BBMV) of human full term placenta and identified functional groups of the carrier proteins that are important for transport function. Alanine influx into BBMV was found to be mediated by two transport systems with different kinetic features and distinct substrate specificities. An uphill operating electrogenic Na(+)-dependent cotransport system could be kinetically separated from a Na(+)-independent facilitated diffusion system. The Na(+)-dependent transporter mediates Na(+)-alanine cotransport with a 1:1 flux coupling ratio (Hill coefficient 1.13 +/- 0.12) and a Km for alanine of 0.45 +/- 0.06 mmol/l. Half-maximal stimulation of Na(+)-dependent alanine influx was observed at a Na+ concentration (NaCl) of 51.4 +/- 1.3 mmol/l. A variety of group specific reagents were used to identify functional groups in the transport proteins. Only compounds reacting with SH-residues (NEM, DTNB, PCMBS) or NH2-groups (PITC) were found to affect Na+ dependent and Na+ independent alanine transport. The EC50 value for inhibition of alanine influx by PCMBS was 450 +/- 48 mumol/l. Chemical modifications of SH-groups by PCMBS caused a significant reduction (p < 0.005) in the Vmax for Na(+)-dependent alanine influx from 0.57 +/- 0.06 to 0.16 +/- 0.05 nmol.mg protein-1.10s-1 without affecting significantly the Km value. Inhibition by PCMBS was reversed by treatment of BBMV with DTT. When the substrate binding site of the transporter was protected by alanine or leucine, PCMBS still, blocked transport function, indicating that the crucial SH groups are not located within the substrate binding site of the transport proteins.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Dec
pubmed:issn
0044-264X
pubmed:author
pubmed:issnType
Print
pubmed:volume
34
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
285-92
pubmed:dateRevised
2004-11-17
pubmed:meshHeading
pubmed:year
1995
pubmed:articleTitle
Alanine transport across the human placental brush border membrane and the role of SH groups in carrier function.
pubmed:affiliation
AG Biochemie der Ernährung, Institut für Ernährungswissenschaft, Justus-Liebig-Universität Giessen.
pubmed:publicationType
Journal Article