title: Glutathione S-transferase in adult Dirofilaria immitis and Brugia pahangi.
abstract: Glutathione S-transferase (EC 2.5.1.18) was detected in the cytosolic and microsomal fractions of adult Dirofilaria immitis females at respective levels of 30 nmol and 3 nmol min-1 (mg protein)-1 activity with the substrate 1-chloro-2,4-dinitrobenzene (CDNB). The transferase activity in the cytosolic fraction of adult Brugia pahangi females was 10 nmol min-1 mg-1 with CDNB; determination of its activity in the microsomal fraction of this filariid was not attempted. These filarial glutathione S-transferases were further characterized after their purification by glutathione-affinity chromatography. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the cytosolic transferase from D. immitis, molecular weight 47000, yielded a single subunit of around 28 kDa. The cytosolic and microsomal transferases from D. immitis differed in their activity with CDNB, 1,2-dichloro-4-nitrobenzene, 4-benzylchloride and ethacrynic acid. The cytosolic transferase from B. pahangi was distinguished by its high activity with ethacrynic acid. Both glutathione S-transferases from D. immitis also functioned as a glutathione peroxidase, strongly preferring cumene hydroperoxide as a substrate over hydrogen peroxide. Both were equiactive inhibitors of malonaldehyde formation in the NADPH-microsomal lipid peroxidation system. Thus, in addition to the ability of filarial glutathione S-transferases to detoxify electrophilic xenobiotics, at least those from D. immitis also exhibited selenium-independent glutathione peroxidase activity. Their glutathione S-transferase function suggests a potential role for these enzymes in the leukotriene synthetic pathway, if filariae can form such eicosanoids from arachidonate. Functioning as a glutathione peroxidase, they could serve to protect filarial membrane lipids from peroxidation.
mesh_terms: D000818:Animals; D002009:Brugia / Q000201:enzymology*; D002846:Chromatography, Affinity; D004137:Dinitrochlorobenzene / Q000378:metabolism; D004183:Dirofilaria immitis / Q000201:enzymology*; D004591:Electrophoresis, Polyacrylamide Gel; D004976:Ethacrynic Acid / Q000378:metabolism; D005260:Female; D005370:Filarioidea / Q000201:enzymology*; D005982:Glutathione Transferase / Q000302:isolation & purification / Q000378:metabolism*; D008862:Microsomes, Liver / Q000201:enzymology; D008970:Molecular Weight; D009578:Nitrobenzenes / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D004137:Dinitrochlorobenzene; D009578:Nitrobenzenes; C027562:4-nitrobenzyl chloride; C028328:1,2-dichloro-4-nitrobenzene; D005982:Glutathione Transferase; D004976:Ethacrynic Acid