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Ascorbyl free radical and dehydroascorbate formation in rat liver endoplasmic reticulum

Szarka, Andras; Stadler, Krisztian; Jenei, Veronica LU ; Margittai, Eva; Csala, Miklos; Jakus, Judit; Mandl, Jozsef and Banhegyi, Gabor (2002) In Journal of Bioenergetics and Biomembranes 34(4). p.317-323
Abstract
The mechanism of ascorbate oxidation was studied in rat liver microsomes. A continuous consumption of the added ascorbate was observed, which was accompanied with a prompt appearance of ascorbyl free radical and dehydroascorbate. Microsomes sustained steady-state level of ascorbyl free radical and dehydroascorbate till ascorbate was present in the medium. Ascorbyl free radical formation was diminished when microsomes had been pretreated with heat or trypsine. It was also decreased by addition of quercetin, econazole or metal chelators, including the copper specific neocuproine. Enzymatic (superoxide dismutase, catalase) and nonenzymatic (dimethyl sulfoxide, mannitol) antioxidants did not modify the microsomal production of ascorbyl free... (More)
The mechanism of ascorbate oxidation was studied in rat liver microsomes. A continuous consumption of the added ascorbate was observed, which was accompanied with a prompt appearance of ascorbyl free radical and dehydroascorbate. Microsomes sustained steady-state level of ascorbyl free radical and dehydroascorbate till ascorbate was present in the medium. Ascorbyl free radical formation was diminished when microsomes had been pretreated with heat or trypsine. It was also decreased by addition of quercetin, econazole or metal chelators, including the copper specific neocuproine. Enzymatic (superoxide dismutase, catalase) and nonenzymatic (dimethyl sulfoxide, mannitol) antioxidants did not modify the microsomal production of ascorbyl free radical. Investigation of the subcellular distribution of ascorbate oxidation showed that the microsomal fraction of liver had the highest activity. The decrease of ascorbate oxidation after protease treatment and the negligible increase upon permeabilization of microsomal vesicles showed that a membrane protein is responsible for the activity, which is exposed to the outer surface of the endoplasmic reticulum. The results indicate the presence of a primary enzymatic ascorbate oxidation in rat liver endoplasmic reticulum which is able to generate dehydroascorbate, an important source of the oxidizing environment in the endoplasmic reticulum. (Less)
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author
publishing date
type
Contribution to journal
publication status
published
subject
in
Journal of Bioenergetics and Biomembranes
volume
34
issue
4
pages
317 - 323
publisher
Kluwer
external identifiers
  • pmid:12392195
  • scopus:0036698219
ISSN
1573-6881
DOI
10.1023/A:1020212720330
language
English
LU publication?
no
id
56f29f6e-17a2-4707-8336-4587cb4a48cb (old id 1124535)
date added to LUP
2008-06-03 12:03:41
date last changed
2017-06-25 03:36:37
@article{56f29f6e-17a2-4707-8336-4587cb4a48cb,
  abstract     = {The mechanism of ascorbate oxidation was studied in rat liver microsomes. A continuous consumption of the added ascorbate was observed, which was accompanied with a prompt appearance of ascorbyl free radical and dehydroascorbate. Microsomes sustained steady-state level of ascorbyl free radical and dehydroascorbate till ascorbate was present in the medium. Ascorbyl free radical formation was diminished when microsomes had been pretreated with heat or trypsine. It was also decreased by addition of quercetin, econazole or metal chelators, including the copper specific neocuproine. Enzymatic (superoxide dismutase, catalase) and nonenzymatic (dimethyl sulfoxide, mannitol) antioxidants did not modify the microsomal production of ascorbyl free radical. Investigation of the subcellular distribution of ascorbate oxidation showed that the microsomal fraction of liver had the highest activity. The decrease of ascorbate oxidation after protease treatment and the negligible increase upon permeabilization of microsomal vesicles showed that a membrane protein is responsible for the activity, which is exposed to the outer surface of the endoplasmic reticulum. The results indicate the presence of a primary enzymatic ascorbate oxidation in rat liver endoplasmic reticulum which is able to generate dehydroascorbate, an important source of the oxidizing environment in the endoplasmic reticulum.},
  author       = {Szarka, Andras and Stadler, Krisztian and Jenei, Veronica and Margittai, Eva and Csala, Miklos and Jakus, Judit and Mandl, Jozsef and Banhegyi, Gabor},
  issn         = {1573-6881},
  language     = {eng},
  number       = {4},
  pages        = {317--323},
  publisher    = {Kluwer},
  series       = {Journal of Bioenergetics and Biomembranes},
  title        = {Ascorbyl free radical and dehydroascorbate formation in rat liver endoplasmic reticulum},
  url          = {http://dx.doi.org/10.1023/A:1020212720330},
  volume       = {34},
  year         = {2002},
}