Uncoupled redox systems in the lumen of the endoplasmic reticulum. Pyridine nucleotides stay reduced in an oxidative environment.
The redox state of the intraluminal pyridine nucleotide pool was investigated in rat liver microsomal vesicles. The vesicles showed cortisone reductase activity in the absence of added reductants, which was dependent on the integrity of the membrane. The intraluminal pyridine nucleotide pool could be oxidized by the addition of cortisone or metyrapone but not of glutathione. On the other hand, intraluminal pyridine nucleotides were slightly reduced by cortisol or glucose 6-phosphate, although glutathione was completely ineffective. Redox state of microsomal protein thiols/disulfides was not altered either by manipulations affecting the redox state of pyridine nucleotides or by the addition of NAD(P)+ or NAD(P)H. The uncoupling of the thiol/disulfide and NAD(P)+/NAD(P)H redox couples was not because of their subcompartmentation, because enzymes responsible for the intraluminal oxidoreduction of pyridine nucleotides were distributed equally in smooth and rough microsomal subfractions. Instead, the phenomenon can be explained by the negligible representation of glutathione reductase in the endoplasmic reticulum lumen. The results demonstrated the separate existence of two redox systems in the endoplasmic reticulum lumen, which explains the contemporary functioning of oxidative folding and of powerful reductive reactions.
Piccirella
Simona
S
Department of Medical Chemistry, Molecular Biology, and Pathobiochemistry, Semmelweis University, Budapest, Hungary.
Czegle
Ibolya
I
Lizák
Beáta
B
Margittai
Eva
E
Senesi
Silvia
S
Papp
Eszter
E
Csala
Miklós
M
Fulceri
Rosella
R
Csermely
Péter
P
Mandl
József
J
Benedetti
Angelo
A
Bánhegyi
Gábor
G
D043205:11-beta-Hydroxysteroid Dehydrogenase Type 1 / Q000378:metabolism; D000818:Animals; D001692:Biological Transport; D015153:Blotting, Western; D002237:Carbohydrate Dehydrogenases / Q000737:chemistry; D003349:Cortisone Reductase / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D019298:Glucose-6-Phosphate / Q000737:chemistry; D005978:Glutathione / Q000378:metabolism; D005980:Glutathione Reductase / Q000737:chemistry; D006854:Hydrocortisone / Q000737:chemistry; D008027:Light; D008297:Male; D008862:Microsomes, Liver / Q000378:metabolism*; D009249:NADP / Q000737:chemistry; D019255:NADPH Oxidases / Q000378:metabolism; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism*; D011725:Pyridines / Q000737:chemistry*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012542:Scattering, Radiation; D013050:Spectrometry, Fluorescence; D013347:Subcellular Fractions; D013696:Temperature; D013997:Time Factors
D011725:Pyridines; D009249:NADP; D019298:Glucose-6-Phosphate; D002237:Carbohydrate Dehydrogenases; C020552:galactose-6-phosphate dehydrogenase; D043205:11-beta-Hydroxysteroid Dehydrogenase Type 1; D003349:Cortisone Reductase; D019255:NADPH Oxidases; D005980:Glutathione Reductase; D005978:Glutathione; C023666:pyridine; D010100:Oxygen; D006854:Hydrocortisone