Subcellular distribution and activities of superoxide dismutase, catalase, glutathione peroxidase, and glutathione reductase in the southern armyworm, Spodoptera eridania

Abstract

In mid-fifth-instar larvae of the southern armyworm, Spodoptera eridania, the subcellular distribution of four antioxidant enzymes-superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPOX), and glutathione reductase (GR)-were examined. Two-thirds (4.26 units -mg protein-') of the SOD activity was found in the cytosol, and one-third (2.13 units -mg protein-') in the mitochondria. CAT activity was unusually high and not restricted to the microsomal fraction where peroxisomes are usually isolated. The activity was distributed as follows: cytosol (163 units) mitochondria (125 units) and microsomes (119 units). Similar to CAT, the subcellular compartmentalization of both GPOX and GR was unusual. N o activity was detected in the cytosol, but in mitochondria and microsornes, GR levels were 5.49 and 3.09 units. Although GPOX activity exhibited 14-16-fold enrichment in mitochondria and microsornes, respectively, over the 850g crude homogenate, the level was negligible (mitochondria = 1.4 x IOW3 units; microsomes = 1.6 x lop3 units), indicating that this enzyme is absent. The,unusual distribution of CAT has apparently evolved as an evolutionary answer to the absence of GR from the cytosol, and the lack of GPOX activity.Key words: antioxidant enzymes, catalase, detoxification of oxyradicals, glutathione peroxidase, glutathione reductase, superoxide dismutase INTRODUCTIONIn all aerobic organisms the superoxide anion free radical is generated through one-electron reduction of dioxygen from numerous biological sources Received October 5,1987; accepted January 6,1988. Address reprint requests to Dr. Sami Ahmad, Department of Biochemistry, University of Nevada, Reno, NV 89557-0014. which include small to large autoxidizable molecules (e.g., catecholamines, hemoproteins), oxidoreductases (e.g ., xanthine oxidase), and subcellular organelles such as nuclei, mitochondria, microsomes, and chloroplasts [l] .Damages from 02-* generating systems have been recently reviewed [2].Further, 0,-in its protonated form, -0OH radical, and the conversion of 0,-via the metal-catalyzed Haber-Weiss reaction (Fenton reaction) produces in vivo H202 and -OH [3]. These products are more reactive than their precursor, and in particular, -OH is very deleterious, as it causes lipid peroxidation [4]. The potential is especially high for harmful consequences of lipid peroxidation in insects in that lipids not only are essential components of cellular membranes but also have unique physiological functions in insects [5].Phytophagous insects are additionally subject to exogenous plant prooxidant sources of toxic oxygen compounds and free radicals. Plant pro-oxidants consist of photodynamically active compounds such as furanocoumarins, e.g., xanthotoxin [6], which mainly generates ' 0 2 and only secondarily some 0,: [q. Phenolic compounds such as flavonoids, e.g., quercetin, generate 0,-and H202 apparently nonphotoactively upon enzymatic bioactivation [8] and these products further generate -OH 191.Among well-known defenses are antioxidant ...

Antioxidant enzymes as biochemical defenses against phototoxin‐induced oxidative stress in three species of herbivorous lepidoptera

“…Even though we observed GR activity in all three species examined, we did not measure significant levels of GPOX using Hz02 as substrate. This result is consistent with the original findings of other researchers [ 17,18,30] who also observed only negligible GPOX activity against this substrate. It has been demonstrated, however, that there exists high levels of GSHdependent peroxidase activity in the cabbage looper T. ni when assayed using the substrate cumOOH instead of H202 [33,34].…”

Effect of cold acclimation on the antioxidant defense system of two larval lepidoptera (noctuidae)

“…In the past ten years, the constitutive activity, ontogenetic changes, sub-cellular distribution, and inducibility of these enzymes have been studied in several species of insects [Ahmad et al, 1988;Pritsos et al, 1988aPritsos et al, , 1988bGrubor-Lajsic et al, 1996]. The present results demonstrate some characteristics of the antioxidant defense systems of two species of insects with different cold-hardiness strategies.…”

Antioxidant enzymes in the honey bee, Apis mellifera

“…Evidence for the dual localization and the existence of SODs with different metal content has also been reported for several lepidopteran species (Ahmad et al, 1988a(Ahmad et al, , 1988b(Ahmad et al, , 1990(Ahmad et al, , 1991.…”

“…Thus, CAT may have been lost during the centrifugation of the tissue homogenates. However, soluble CAT has been found in mammalian (Masters et al, 1986) as well as insect species (Aucoin et al, 1991;Joanisse and Storey, 1996), and larval homogenates of lepidopteran species have been shown to contain substantial CAT activities in mitochondrial, microsomal and cytosol fractions (Ahmad et al, 1988a(Ahmad et al, , 1988b(Ahmad et al, , 1990. The midgut of honey bee workers contains CAT in peroxisomal as well as soluble fractions (Jimenez and Gilliam, 1996).…”