title: Protein-disulfide isomerase- and protein thiol-dependent dehydroascorbate reduction and ascorbate accumulation in the lumen of the endoplasmic reticulum.
abstract: The transport and intraluminal reduction of dehydroascorbate was investigated in microsomal vesicles from various tissues. The highest rates of transport and intraluminal isotope accumulation (using radiolabeled compound and a rapid filtration technique) were found in hepatic microsomes. These microsomes contain the highest amount of protein-disulfide isomerase, which is known to have a dehydroascorbate reductase activity. The steady-state level of intraluminal isotope accumulation was more than 2-fold higher in hepatic microsomes prepared from spontaneously diabetic BioBreeding/Worcester rats and was very low in fetal hepatic microsomes although the initial rate of transport was not changed. In these microsomes, the amount of protein-disulfide isomerase was similar, but the availability of protein thiols was different and correlated with dehydroascorbate uptake. The increased isotope accumulation was accompanied by a higher rate of dehydroascorbate reduction and increased protein thiol oxidation in microsomes from diabetic animals. The results suggest that both the activity of protein-disulfide isomerase and the availability of protein thiols as reducing equivalents can play a crucial role in the accumulation of ascorbate in the lumen of the endoplasmic reticulum. These findings also support the fact that dehydroascorbate can act as an oxidant in the protein-disulfide isomerase-catalyzed protein disulfide formation.
authors.affiliation: Department of Medical Chemistry, Molecular Biology and Pathobiochemistry, Semmelweis University, 1444 Budapest, Hungary.
authors.forename: G
authors.initials: G
authors.lastname: Nardai
authors.forename: L
authors.initials: L
authors.lastname: Braun
authors.forename: M
authors.initials: M
authors.lastname: Csala
authors.forename: V
authors.initials: V
authors.lastname: Mile
authors.forename: P
authors.initials: P
authors.lastname: Csermely
authors.forename: A
authors.initials: A
authors.lastname: Benedetti
authors.forename: J
authors.initials: J
authors.lastname: Mandl
authors.forename: G
authors.initials: G
authors.lastname: Banhegyi
mesh_terms: D000818:Animals; D001205:Ascorbic Acid / Q000737:chemistry / Q000378:metabolism*; D001692:Biological Transport; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000201:enzymology / Q000378:metabolism*; D008297:Male; D008862:Microsomes, Liver / Q000201:enzymology / Q000378:metabolism; D019704:Protein Disulfide-Isomerases / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017208:Rats, Wistar; D013438:Sulfhydryl Compounds / Q000378:metabolism*
chemical_list: D013438:Sulfhydryl Compounds; D019704:Protein Disulfide-Isomerases; D001205:Ascorbic Acid