Thiol-dependent metal-catalyzed oxidation of bovine lens aldose reductase. I. Studies on the modification process.
Bovine lens aldose reductase (alditol: NADP+ oxido-reductase, EC 1.1.1.21) undergoes a thiol-dependent oxidative modification catalyzed by the Fe(II)/Fe(III) redox system. The enzyme is inactivated by various oxygen radical generating systems. However, addition of 2-mercaptoethanol to the oxygen radical generating systems resulted in an initial increase followed by a decrease in the activity of aldose reductase. The net maximal increase in the enzyme activity was observed with 3 mM 2-mercaptoethanol, 0.3 mM FeSO4, and 0.9 mM EDTA, either with or without 1 mM hypoxanthine and 37 mU/ml of xanthine oxidase. The formation of the stable, activated intermediate, ARa, appears to proceed through the reaction between the enzyme and the oxidized form of 2-mercaptoethanol which in the presence of iron, forms a mixed disulfide with a cysteine residue. Reduction of ARa with dithiothreitol released 0.7 mol of 2-mercaptoethanol per mole of enzyme and converted it to a form that resembled the native aldose reductase.
Giannessi
M
M
Dipartimento di Fisiologia e Biochimica, Universitá di Pisa, Italy.
Del Corso
A
A
Cappiello
M
M
Voltarelli
M
M
Marini
I
I
Barsacchi
D
D
Garland
D
D
Camici
M
M
Mura
U
U
D000449:Aldehyde Reductase / Q000737:chemistry / Q000378:metabolism*; D000818:Animals; D002417:Cattle; D002851:Chromatography, High Pressure Liquid; D004492:Edetic Acid / Q000494:pharmacology*; D005296:Ferrous Compounds / Q000494:pharmacology*; D019271:Hypoxanthine; D007042:Hypoxanthines / Q000494:pharmacology; D007700:Kinetics; D007908:Lens, Crystalline / Q000201:enzymology*; D008623:Mercaptoethanol / Q000494:pharmacology*; D013438:Sulfhydryl Compounds / Q000494:pharmacology*; D013816:Thermodynamics; D013997:Time Factors; D014969:Xanthine Oxidase / Q000494:pharmacology
D005296:Ferrous Compounds; D007042:Hypoxanthines; D013438:Sulfhydryl Compounds; D019271:Hypoxanthine; C020748:ferrous sulfate; D008623:Mercaptoethanol; D004492:Edetic Acid; D000449:Aldehyde Reductase; D014969:Xanthine Oxidase