| 8424675 |
Giannessi M, Del Corso A, Cappiello M, Voltarelli M, Marini I, Barsacchi D, Garland D, Camici M, Mura U: Thiol-dependent metal-catalyzed oxidation of bovine lens aldose reductase. Arch Biochem Biophys. 1993 Jan;300(1):423-9.
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. |
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