Linked Life Data

2778796

Source:http://linkedlifedata.com/resource/pubmed/id/2778796

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PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
3
pubmed:dateCreated
1989-10-18
pubmed:abstractText
The experiments reported in this paper aim at characterizing the carboxylic acid transport, the interactions of pyruvate and citrate with their transport sites and specificity. The study of these carriers was performed using isotopic solutes for the influx measurements in brush-border membrane vesicles under zero trans conditions where the membrane potential was abolished with KCl preloading with valinomycin or equilibrium exchange conditions and delta psi = 0. Under zero trans condition and delta psi = 0, the influence of pyruvate concentrations on its initial rates of transport revealed the existence of two families of pyruvate transport sites, one with a high affinity for pyruvate (Kt = 88 microM) and a low affinity for sodium (Kt = 57.7 mM) (site I), the second one with a low affinity for pyruvate (Kt = 6.1 mM) and a high affinity for sodium (Kt = 23.9 mM) (site II). The coupling factor [Na]/[pyruvate] stoichiometry were determined at 0.25 mM and 8 mM pyruvate and estimated at 1.8 for site I, and 3 when the first and the second sites transport simultaneously. Under chemical equilibrium (delta psi congruent to 0) single isotopic labeling, transport kinetics of pyruvate carrier systems have shown a double interaction of pyruvate with the transporter; the sodium/pyruvate stoichiometry also expressed according to a Hill plot representation was n = 1.7. The direct method of measuring Na+/pyruvate stoichiometry from double labeling kinetics and isotopic exchange, for a time course, gives a n = 1.67. Studies of transport specificity, indicate that the absence of inhibition of lactate transport by citrate and the existence of competitive inhibition of lactate and citrate transports by pyruvate leads to the conclusion that the low pyruvate affinity site can be attributed to the citrate carrier (tricarboxylate) and the high pyruvate affinity site to the lactate carrier (monocarboxylate).
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Jun
pubmed:issn
0022-2631
pubmed:author
pubmed:issnType
Print
pubmed:volume
108
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
197-205
pubmed:dateRevised
2003-11-14
pubmed:meshHeading
pubmed:year
1989
pubmed:articleTitle
Characterization of sodium and pyruvate interactions of the two carrier systems specific of mono- and di- or tricarboxylic acids by renal brush-border membrane vesicles.
pubmed:affiliation
Laboratoire de Biochimie, Faculté de Médecine, Nice, France.
pubmed:publicationType
Journal Article