Isolated Durum Wheat and Potato Cell Mitochondria Oxidize Externally Added NADH Mostly via the Malate/Oxaloacetate Shuttle with a Rate That Depends on the Carrier-Mediated Transport1
AUTOR(ES)
Pastore, Donato
FONTE
The American Society for Plant Biologists
RESUMO
We investigated whether and how mitochondria from durum wheat (Triticum durum Desf.) and potato (Solanum tuberosum), isolated from etiolated shoots and a cell suspension culture, respectively, oxidize externally added NADH via the mitochondrial shuttles; in particular, we compared the shuttles and the external NADH dehydrogenase (NADH DHExt) with respect to their capacity to oxidize external NADH. We found that external NADH and NADPH can be oxidized via two separate DHExt, whereas under conditions in which the activities of NAD(P)H DHExt are largely prevented, NADH (but not NADPH) is oxidized in the presence of external malate (MAL) and MAL dehydrogenase, in a manner sensitive to several non-penetrant compounds according to the occurrence of the MAL/oxaloacetate (OAA) shuttle. In durum wheat mitochondria and potato cell mitochondria, the rate of NADH oxidation was limited by the rate of a novel carrier, the MAL/OAA antiporter, which is different from other carriers thought to transport OAA across the mitochondrial membrane. No NAD(P)H oxidation occurred arising from the MAL/Aspartate and the α-glycerophosphate/dihydroxyacetonphosphate shuttles. We determined the kinetic parameters of the enzymes and the antiporter involved in NADH oxidation, and, on the basis of a kinetic analysis, we showed that, at low physiological NADH concentrations, oxidation via the MAL/OAA shuttle occurred with a higher efficiency than that due to the NADH DHExt (about 100- and 10-fold at 1 μm NADH in durum wheat mitochondria and in potato cell mitochondria, respectively). The NADH DHExt contribution to NADH oxidation increased with increasing NADH concentration.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=300754Documentos Relacionados
- Small Molecular Drug Transfer across the Blood-Brain Barrier via Carrier-Mediated Transport Systems
- Fatty acid uptake by isolated rat heart myocytes represents a carrier-mediated transport process.
- Light-induced, carrier-mediated transport of tetracycline by Rhodopseudomonas sphaeroides.
- THE KINETICS OF CARRIER-MEDIATED ACTIVE TRANSPORT OF AMINO ACIDS*
- Sugar Accumulation in Sugarcane: Carrier-mediated Active Transport of Glucose