A functional analysis of Kluyveromyces lactis glutathione reductase.

Glutathione reductase (GLR) null mutants of the yeast Kluyveromyces lactis, a model eukaryotic respiratory cell, were created and phenotypically analysed. We found that cells lacking GLR show decreased resistance to oxidative stress and higher levels of reactive oxygen species and catalase activity than the wild-type strain. However, glutathione redox levels (GSH : GSSG ratio) were similar in the DeltaKlglr1 mutant and wild-type strains. The thioredoxin-thioredoxin reductase system is proposed as an alternative system for maintaining the GSH : GSSG ratio in the DeltaKlglr1 mutant. The involvement of GLR in glucose metabolism in K. lactis is suggested by the improved growth on glucose caused by the DeltaKlglr1 mutation and by the increased GLR activity in the DeltaKlgcr1 strain, KlGcr1 being a transcriptional activator of glycolytic genes. We also studied the subcellular location of GLR in K. lactis, showing that it is present in mitochondria; however, the DeltaKlglr1 mutation does not affect mitochondrial morphology. Genomic DNA integrity and life span are also unaffected by the DeltaKlglr1 mutation, at least under the conditions tested in this study.