Linked Life Data

12034470

Source:http://linkedlifedata.com/resource/pubmed/id/12034470

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
1-2
pubmed:dateCreated
2002-5-29
pubmed:abstractText
We have previously provided evidence that diffusion of metabolites across the porin pores of mitochondrial outer membrane is hindered. A functional consequence of this diffusion limitation is the dynamic compartmentation of ADP in the intermembrane space. These earlier studies were done on isolated mitochondria suspended in isotonic media without macromolecules, in which intermembrane space of mitochondria is enlarged. The present study was undertaken to assess the diffusion limitation of outer membrane in the presence of 10% (w/v) dextran M20, in order to mimic the action of cytosolic macromolecules on mitochondria. Under these conditions, mitochondria have a more native, condensed configuration.Flux-dependent concentration gradients of ADP were estimated by measuring the ADP diffusion fluxes across the porin pores of isolated rat heart mitochondria incubated together with pyruvate kinase (PK), both of which compete for ADP regenerated by mitochondrial creatine kinase (mtCK) within the intermembrane space or by yeast hexokinase (HK) extramitochondrially. From diffusion fluxes and bulk phase concentrations of ADP, its concentrations in the intermembrane space were calculated using Fick's law of diffusion. Flux-dependent gradients up to 23 microM ADP (for a diffusion rate of J(Dif)=1.9 micromol ADP/min/mg mitochondrial protein) were observed. These gradients are about twice those estimated in the absence of dextran and in the same order of magnitude as the cytosolic ADP concentration (30 microM), but they are negligibly low for cytosolic ATP (5 mM). Therefore, it is concluded that the dynamic ADP compartmentation is of biological importance for intact heart cells. If mtCK generates ADP within the intermembrane space, the local ADP concentration can be clearly higher than in the cytosol resulting in higher extramitochondrial phosphorylation potentials. In this way, mtCK contributes to ensure optimal kinetic conditions for ATP-splitting reactions in the extramitochondrial compartment.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Apr
pubmed:issn
0006-3002
pubmed:author
pubmed:issnType
Print
pubmed:day
22
pubmed:volume
1554
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
48-56
pubmed:dateRevised
2009-11-3
pubmed:meshHeading
pubmed:year
2002
pubmed:articleTitle
The quantitation of ADP diffusion gradients across the outer membrane of heart mitochondria in the presence of macromolecules.
pubmed:affiliation
Muskellabor der Neurologischen Klinik und Poliklinik, Martin-Luther-Universität, Halle-Wittenberg, Julius-Kühn-Str. 7, D-06097 Halle/Saale, Halle-Wittenberg, Germany. frank.gellerich@medizin.uni-halle.de
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't