The flavin requirement and some inhibition characteristics of rat tissue glutathione reductase.

The characteristics of glutathione reductase have been investigated with preparations from a number of plant and animal sources. A specific requirement for flavin adenine dinucleotide has been demonstrated for this enzyme in pea seed and Escherichiu coli preparations (1, 2), and spectral evidence for an undissociable, unidentified flavin has been presented for the yeast enzyme (3). Although crystalline forms of this enzyme have been prepared from both yeast and rat liver (4, 5), no evidence for a flavin prosthetic group in these preparations has been presented. In the course of an investigation of the mechanism of inhibition of glutathione reductase by nitrofurantoinr (N-(5nitro-2-furfurylidene)-l-aminohydantoin) (6), we have found that the enzyme from rat erythrocytes, liver, and kidney can be inactivated by acid treatment and that activity is restored specifically by the addition of flavin adenine dinucleotide. These results are the first indication that the glutathione reductase of animal tissues is a flavoenzyme. This study also has demonstrated that a variety of nitrobenzene and nitrofuran compounds are powerful, reversible inhibitors of glutathione reductase. Some of the characteristics of inhibition by these compounds have been investigated.