A STRESS-ASSOCIATED CITRUS PROTEIN IS A DISTINCT PLANT PHOSPHOLIPID HYDROPEROXIDE GLUTATHIONE-PEROXIDASE

A protein whose level is markedly increased upon exposure of cultured citrus cells and whole plants to NaCl, was shown to specifically catal yze the reduction of phosphatidylcholine hydroperoxide in the presence of glutathione. This enzymatic activity was shown to be independent o f a similar activity exhibited by glutathione S-transferase in plants. This finding corroborates the significant homology (52%) accounted be tween the deduced amino acid sequence of the gene encoding for this pr otein and that of mammalian phospholipid hydroperoxide glutathione per oxidases. While the mammalian enzyme is known and well investigated, t his study establishes the presence of this key protein also in plants.