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Glutathione peroxidase activity in insects: A reassessment
Author(s) -
Ahmad Sami,
Beilstein Michael A.,
Pardini Ronald S.
Publication year - 1989
Publication title -
archives of insect biochemistry and physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.576
H-Index - 66
eISSN - 1520-6327
pISSN - 0739-4462
DOI - 10.1002/arch.940120104
Subject(s) - biology , glutathione peroxidase , peroxidase , housefly , selenoprotein , biochemistry , endocrinology , medicine , catalase , antioxidant , botany , enzyme , musca , larva
In vertebrate species, cytotoxic H 2 O 2 and other lipid or organic hydroperoxides (ROOH) formed in aerobic metabolism are removed by a selenoprotein, glutathione peroxidase (GPOX). The GPOX activity in most rat tissues ranges from 100 to 1,000 units (1 unit = 1 nmol NADPH oxidized·mg protein −1 ·min −1 ), except for muscles (20–30 units). In contrast, GPOX activities of two strains of the housefly ( Musca domestica ), cabbage looper ( Trichoplusia ni ), southern armyworm ( Spodoptera eridania ), and black swallowtail butterfly ( Papilio polyxenes ), were found to be in the range 2–12 units. Trivial GPOX activity was detected in the confused flour beetle ( Tribolium confusum ). In the earthworm ( Lumbricus terrestris ), banana slug ( Ariolimax columbianus ), and market squid ( Loligo opalescens ), the GPOX activity ranged from 1 to 5 units. Tissue selenium concentrations were about 500–1,000 ppb for adult M. domestica , 600 ppb in T. confusum , 32 ppb in T. ni , 17 ppb in S. eridania , and 31 ppb in P. polyxenes larvae. The form of selenium incorporated at such high levels in tissues of invertebrates such as M. domestica remains an unresolved issue. Peroxidase activity of non‐selenium glutathione‐S‐transferase (GT) against ROOH may compensate for the low GPOX activity. Catalase (CAT) has high activity and wide subcellular distribution in insects. This may be an evolutionary adaptation to GT's inability to catalyze the reduction of H 2 O 2 . The GT's peroxidase and CAT activities were not assessed for other invertebrate species, and warrants an investigation due to their reported low GPOX levels.