The Inter-Relationship of Ascorbate Transport, Metabolism and Mitochondrial, Plastidic Respiration

Abstract

Significance: Ascorbate, this multifaceted small molecular weight carbohydrate derivative, plays important roles in a range of cellular processes in plant cells, from the regulation of cell cycle, through cell expansion and senescence. Beyond these physiological functions, ascorbate has a critical role in responses to abiotic stresses, such as high light, high salinity, or drought. The biosynthesis, recycling, and intracellular transport are important elements of the balancing of ascorbate level to the always-changing conditions and demands. Recent Advances: A bidirectional tight relationship was described between ascorbate biosynthesis and the mitochondrial electron transfer chain (mETC), since L-galactono-1,4-lactone dehydrogenase (GLDH), the enzyme catalyzing the ultimate step of ascorbate biosynthesis, uses oxidized cytochrome c as the only electron acceptor and has a role in the assembly of Complex I. A similar bidirectional relationship was revealed between the photosynthetic apparatus and ascorbate biosynthesis since the electron flux through the photosynthetic ETC affects the biosynthesis of ascorbate and the level of ascorbate could affect photosynthesis. Critical Issues: The details of this regulatory network of photosynthetic electron transfer, respiratory electron transfer, and ascorbate biosynthesis are still not clear, as are the potential regulatory role and the regulation of intracellular ascorbate transport and fluxes. Future Directions: The elucidation of the role of ascorbate as an important element of the network of photosynthetic, respiratory ETC and tricarboxylic acid cycle will contribute to understanding plant cell responses to different stress conditions.

Intracellular Redox Compartmentation and ROS-Related Communication in Regulation and Signaling

“…Nevertheless, work over recent decades has demonstrated the uptake of ascorbate and glutathione into cells or subcellular organelles at rates well in excess of diffusion. Because of space limitations, we refer the reader to studies cited in other recent articles (Maughan et al, 2010;Noctor et al, 2013;Szarka et al, 2013;Fernie and Tóth, 2015;Foyer, 2015). With the exceptions noted below, many of the transporters remain to be characterized at the molecular level.…”

“…Indeed, the mitochondria are rich in glutathione (Zechmann et al, 2008), despite little evidence that they can produce this compound. Although mitochondria are the site of the final step of ascorbate synthesis, the compound is produced in the intermembrane space, meaning that import into the matrix is required (Szarka et al, 2013). Several lines of evidence suggest that ascorbate may cross the inner mitochondrial membrane as the oxidized form, dehydroascorbate (DHA; Szarka et al, 2013).…”

“…Although mitochondria are the site of the final step of ascorbate synthesis, the compound is produced in the intermembrane space, meaning that import into the matrix is required (Szarka et al, 2013). Several lines of evidence suggest that ascorbate may cross the inner mitochondrial membrane as the oxidized form, dehydroascorbate (DHA; Szarka et al, 2013). DHA also can be transported across the plasma membrane, while ascorbate is exported from the cell interior to replenish the pool present in the apoplast (Fig.…”

Vízoldaható antioxidánsok döntéshelyzetben

“…A kerülõút limitáló lépése nagy valószínûség szerint az aszkorbát mátrixból történõ kijutása. Ezt bizonyítja, hogy a DHA redukció eredményeként keletkezõ aszkorbát a mátrixhoz képest jelentõs késedelemmel jelenik csak meg az extramitokondriális térben (mitokondriális membránközti térben) 23 .…”

Caracaterização cinética da redução das 1-Cys Peroxirredoxinas por ascorbato

“…A enzima oxida o substrato Galactono-1,4-lactona utilizando o citocromo C oxidado como aceptor final de elétrons (Smirnoff, 2000;Szarka, 2013). Posteriormente o ascorbato é oxidado a DHA pela enzima ascorbato peroxidase (APX) e transferido para a matriz mitocondrial pelos GLUT.…”