PMID: 8585244Dec 1, 1995Paper

Alanine transport across the human placental brush border membrane and the role of SH groups in carrier function

Zeitschrift für Ernährungswissenschaft
A SchollH Daniel

Abstract

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 ...Continue Reading

References

Jan 1, 1992·Annual Review of Nutrition·C H SmithV Ganapathy
Dec 1, 1990·Biochemical Society Transactions·D L Yudilevich, L F Barros
Jan 1, 1989·Biology of the Neonate·F C Battaglia
Mar 1, 1989·The American Journal of Physiology·S D Hoeltzli, C H Smith
Jun 1, 1988·The American Journal of Physiology·L W Johnson, C H Smith
Aug 15, 1986·The Biochemical Journal·M E GanapathyV Ganapathy
Sep 9, 1985·Biochimica Et Biophysica Acta·D L Yudilevich, J H Sweiry

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