The oxidation of glutathione by a lipoxidase enzyme from pea seeds

Abstract

Under certain conditions a rapid oxidation of glutathione (GSH) was seen when it was added to a dialyzed extract from ungerminated peas. The reaction was due to a coupled oxidation of the sulfydryl compound and an unsaturated fatty acid of the linoleic acid type by a lipoxidase enzyme. These extracts showed no evidence of lipoxidase activity as judged by O2 consumption or ability to oxidize GSH. The enzymic activity of the extract could be initiated by addition of small amounts of certain alcohols. The alcohols were shown to act by altering the condition of the fatty acid substrate in such a way that it is made accessible to the enzyme. During germination, similar changes occur. The relation between chemical structure of the alcohols and their ability to initiate the lipoxidase reaction was studied, and the mechanism of their action discussed. The lipoxidase enzyme and substrate were associated with the soluble part of the cytoplasm and were absent from the mitochondria. Coupled oxidation of GSH was the result of 2 reactions, one of which was cyanide-sensitive and the other cyanide-insensitive. There is evidence that in the former reaction a metal catalyst is involved.