Glutathione S-transferases in earthworms (Lumbricidae)

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Abstract
Glutathione S-transferase activity (EC 2.5.1.18) was demonstrated in 6 spp. of earthworms of the family Lumbricidae: Eisenia foetida, Lumbricus terrestris, L. rubellus, Allolobophora longa, A. caliginosa and A. chlorotica. Considerable activity was obtained with 1-chloro-2,4-dinitrobenzene and low activity with 3,4-dichloro-1-nitrobenzene, but no enzymic reaction was detectable with sulphobromophthalein, 1,2-epoxy-3-(p-nitrophenoxy)propane or trans-4-phenylbut-3-en-2-one as substrates. Enzyme preparations from L. rubellus and A. longa were the most active, whereas A. chlorotica gave the lowest activity. The ratio of the activities obtained with 1-chloro-2,4-dinitrobenzene and 3,4-dichloro-1-nitrobenzene was very different in the various species, but no phylogenetic pattern was evident. Isoelectric focusing facilitated various activity peaks as measured with 1-chloro-2,4-dinitrobenzene as a substrate. The activity profiles of the species examined appeared to follow a taxonomic pattern. Allolobophora had the highest peak in the alkaline region, whereas Lumbricus had the highest peak in the acid region. Eisenia showed a very complex activity profile, with the highest peak near pH 7. An enzymic assay determined that all the species contained glutathione, on an average of approximately 0.5 .mu.mol/g wet wt. Conjugation with glutathione catalyzed by glutathione S-transferases may consequently be an important detoxification mechanism in earthworms.