Superoxide-dependence of the short chain sugars-induced mutagenesis

Short chain sugars such as glycolaldehyde are produced at the initial stages of nonenzymatic glycosylation. Because their carbonyl groups cannot be blocked by cyclization, such compounds tautomerize to enediols, which are prone to autoxidation. Superoxide radical serves as an initiator and a propagator of this autoxidation. The biological importance of the involvement of superoxide in sugar autoxidation in vivo was examined using superoxide dismutase (SOD)-deficient and SOD-replete strains of Escherichia coli. Glycolaldehyde, glyceraldehyde, and dihydroxyacetone greatly enhanced the mutation rates in SOD-deficient E. coli. The effect was oxygen-dependent and was suppressed by SOD or by a SOD mimetic. The mutagenic effect of glycolaldehyde coincided with intracellular accumulation of glyoxal, a product of glycolaldehyde autoxidation.     

Induction of the soxRS regulon of Escherichia coli by glycolaldehyde

The ability of short-chain sugars to cause oxidative stress has been examined using glycolaldehyde as the simplest sugar. Short-chain sugars autoxidize in air, producing superoxide and alpha,beta-dicarbonyls. In Escherichia coli the soxRS regulon mediates an oxidative stress response, which protects the cell against both superoxide-generating agents and nitric oxide. In superoxide dismutase-deficient E. coli mutants, glycolaldehyde induces fumarase C and nitroreductase A, which are regulated as members of the soxRS regulon. A mutational defect in soxRS eliminates that induction. This establishes that glycolaldehyde can cause induction of this defensive regulon. This effect of glycolaldehyde was oxygen-dependent, was not shown by glyoxal, and was not seen in the superoxide dismutase-replete parental strain, and it was abolished by a cell-permeable SOD mimetic. All of these suggest that superoxide radicals produced by the oxidation of glycolaldehyde played a key role in the induction.     

Characteristics of mutagenesis by glyoxal in Salmonella typhimurium: contribution of singlet oxygen

The characteristics of mutagenesis by glyoxal in Salmonella tester strains TA100 and TA104, and particularly a possible role of active oxygen species, were investigated. Glyoxal was converted into a non-mutagenic chemical with glutathione (GSH) by glyoxalase I, and the mutagenic activity was enhanced by the depletion of intracellular GSH. Glyoxal caused the reduction of nitro blue tetrazolium, which was suppressed by the addition of 2,5-diphenylfuran, superoxide dismutase (SOD) and catalase (CAT), scavengers of singlet oxygen (1O2), superoxide radical (O2-) and hydrogen peroxide (H2O2), respectively. However, only the 1O2 scavenger almost completely suppressed the mutagenic activity of glyoxal. Mutagenicity assays using strains pretreated with N,N-diethyldithiocarbamate of a SOD inhibitor and strains with low levels of SOD and CAT indicated that the mutagenesis by glyoxal was independent of intracellular levels of SOD and CAT, though glyoxal itself repressed them. Therefore, all the results suggest that 1O2 formed from glyoxal is related to its mutagenesis, but that neither O2- nor H2O2 is intracellularly predominantly related to it. The action of glyoxal against SOD and CAT, and the formation of glyoxal adducts with amino acids as their components are also discussed.     

Cytotoxic molecular mechanisms and cytoprotection by enzymic metabolism or autoxidation for glyceraldehyde, hydroxypyruvate and glycolaldehyde

Previously, we showed that dietary fructose or its carbonyl metabolites, glyceraldehyde and glycolaldehyde, could be oxidized by inflammatory reactive oxygen species (ROS), products of immune cells, to form highly toxic and genotoxic products, such as glyoxal. Glycolaldehyde-caused hepatocyte protein carbonylation likely resulted from glyoxal, an autoxidation product formed by ROS. Although hepatocyte protein carbonylation by glyoxal or d-glycolaldehyde was rapid, the product was unstable. Glyceraldehyde-induced protein carbonylation was slower and was also less cytotoxic. Non-toxic concentrations of H(2)O(2) were then used to mimic inflammation and oxidative stress associated with fructose-induced non-alcoholic steatohepatitis (NASH). A slow infusion of H(2)O(2) markedly increased glyoxal, glyceraldehyde, and glycolaldehyde-induced cytotoxicity and protein carbonylation. However, it had a smaller effect on glyceraldehyde-induced protein carbonylation. The cytotoxicities of both aldehydes were increased if glutathione (GSH)-depleted hepatocytes were used, presumably because of the increased ROS formation and subsequent glyoxal-induced protein carbonylation. Catalytic amounts of Cu or Fe increased the glycolaldehyde and glyceraldehyde-induced cytotoxicity and protein carbonylation resulting from autoxidation to glyoxal. Glyceraldehyde and glycolaldehyde were also detoxified by mitochondrial aldehyde dehydrogenase (ALDH2) as ALDH2 inhibitors increased their cytotoxicity. Hydroxypyruvate has not been previously tested for toxicity and was found to be the most toxic fructose metabolite. Catalytic amounts of Cu or Fe caused hydroxypruvate autoxidation, which formed extensive ROS, glycolaldehyde and glyoxal. Iron chelators EGTA or deferoxamine inhibited cytotoxicity as well as the extensive ROS formation. The Girard assay confirmed that glyoxal was a common autoxidation product from glyceraldehyde, glycolaldehyde and hydroxypyruvate.     

Fructose induced deactivation of antioxidant enzymes: preventive effect of pyruvate

Glycation initiated changes in tissue proteins, which are triggered by the Schiff base formation between the sugar carbonyl and the protein -NH2, have been suggested to play an important role in the development of diabetes-related pathological changes such as the formation of cataracts. While the initial reaction takes place by the interaction of >C=O of the parent sugars with the -NH2 of proteins, reactive oxygen species (ROS) dependent generation of more reactive dicarbonyl derivatives from the oxidation of sugars also plays a significant role in these changes, altering the structural as well as functional properties of proteins. The purpose of this study was to examine whether the activities of glyceraldehyde-3-phosphate dehydrogenase (GAPDH), catalase and superoxide dismutase (SOD) could be affected by the high levels of fructose prevalent in diabetic lenses. Incubation of the enzymes with this sugar led to a significant loss of their activities. GAPDH was inactivated within a day. This was followed by the inactivation of catalase (3-4 days) and SOD (6 days). The loss of the activities was prevented significantly by incorporation of pyruvate in the incubation mixture. The protective effect is ascribable to its ability to competitively inhibit glycation as well as to its ROS scavenging activity. Hence, it could play a significant role in the maintenance of lens physiology and cataract prevention.     

Fructose induced deactivation of antioxidant enzymes: Preventive effect of pyruvate

Glycation initiated changes in tissue proteins, which are triggered by the Schiff base formation between the sugar carbonyl and the protein -NH₂, have been suggested to play an important role in the development of diabetes-related pathological changes such as the formation of cataracts. While the initial reaction takes place by the interaction of >C=O of the parent sugars with the -NH₂ of proteins, reactive oxygen species (ROS) dependent generation of more reactive dicarbonyl derivatives from the oxidation of sugars also plays a significant role in these changes, altering the structural as well as functional properties of proteins. The purpose of this study was to examine whether the activities of glyceraldehyde-3-phosphate dehydrogenase (GAPDH), catalase and superoxide dismutase (SOD) could be affected by the high levels of fructose prevalent in diabetic lenses. Incubation of the enzymes with this sugar led to a significant loss of their activities. GAPDH was inactivated within a day. This was followed by the inactivation of catalase (3–4 days) and SOD (6 days). The loss of the activities was prevented significantly by incorporation of pyruvate in the incubation mixture. The protective effect is ascribable to its ability to competitively inhibit glycation as well as to its ROS scavenging activity. Hence, it could play a significant role in the maintenance of lens physiology and cataract prevention.     

Microbial oxidases catalyzing conversion of glycolaldehyde into glyoxal

The present paper reviews oxidases catalyzing conversion of glycolaldehyde into glyoxal. The enzymatic oxidation of glycolaldehyde into glyoxal was first reported in alcohol oxidases (AODs) from methylotrophic yeasts such as Candida and Pichia, and glycerol oxidase (GLOD) from Aspergillus japonicus, although it had been reported that these enzymes are specific to short-chain linear aliphatic alcohols and glycerol, respectively. These enzymes continuously oxidized ethylene glycol into glyoxal via glycolaldehyde. The AODs produced by Aspergillus ochraceus and Penicillium purpurescens also oxidized glycolaldehyde. A new enzyme exhibiting oxidase activity for glycolaldehyde was reported from a newly isolated bacterium, Paenibacillus sp. AIU 311. The Paenibacillus enzyme exhibited high activity for aldehyde alcohols such as glycolaldehyde and glyceraldehyde, but not for methanol, ethanol, ethylene glycol or glycerol. The deduced amino acid sequence of the Paenibacillus AOD was similar to that of superoxide dismutases (SODs), but not to that of methylotrophic yeast AODs. Then, it was demonstrated that SODs had oxidase activity for aldehyde alcohols including glycolaldehyde. The present paper describes characteristics of glycolaldehyde oxidation by those enzymes produced by different microorganisms.     

Immunological evidence that non-carboxymethyllysine advanced glycation end-products are produced from short chain sugars and dicarbonyl compounds in vivo

BACKGROUND: The Maillard reaction that leads to the formation of advanced glycation end-products (AGE) plays an important role in the pathogenesis of angiopathy in diabetic patients and in the aging process. Recently, it was proposed that AGE were not only created by glucose, but also by dicarbonyl compounds derived from the Maillard reaction, autoxidation of sugars and other metabolic pathways of glucose. In this study, we developed four types of non-carboxymethyllysine (CML) anti-AGE antibodies that recognized proteins modified by incubation with short chain sugars and dicarbonyl compounds. MATERIALS AND METHODS: AGE-modified serum albumins were prepared by incubation of rabbit serum albumin with glyceraldehyde, glycolaldehyde, methylglyoxal or glyoxal. After immunization of rabbits, four types of AGE-specific antisera were obtained that were specific for the AGE modification. To separate non-CML AGE antibodies (Ab) (non-CML AGE-Ab-2, -3, -4, and -5), these anti-AGE antisera were subjected to affinity chromatography on a matrix coupled with four kinds of AGE bovine serum albumin (BSA) or CML-BSA. These non-CML AGE antibodies were used to investigate the AGE content of serum obtained from diabetic patients on hemodialysis. RESULTS: Characterization of the four types of non-CML AGE antibodies obtained by immunoaffinity chromatography was performed by competitive ELISA and immunoblot analysis. Non-CML AGE-Ab-2 crossreacted with the protein modified by glyceraldehyde or glycolaldehyde. Non-CML AGE-Ab-3 and -Ab-4 specifically cross-reacted with protein modified by glycolaldehyde and methylglyoxal, respectively. NonCML AGE-Ab-5 cross-reacted with protein modified with glyoxal as well as methylglyoxal and glycolaldehyde. Three kinds of non-CML AGE (AGE-2, -4, and -5) were detected in diabetic serum as three peaks with apparent molecular weights of 200, 1.15, and 0.85 kD; whereas, AGE-3 was detected as two peaks with apparent molecular weights of 200 and 0.85 kD. CONCLUSION: We propose that various types of non-CML AGE are formed by the Maillard reaction, sugar autoxidation and sugar metabolism. These antibodies enable us to identify such compounds created by the Maillard reaction in vivo.     

Generation of a Superoxide Dismutase (SOD)-Deficient Mutant of Campylobacter coli: Evidence for the Significance of SOD in Campylobacter Survival and Colonization

The microaerophilic nature of Campylobacter species implies an inherent sensitivity towards oxygen and its reduction products, particularly the superoxide anion. The deleterious effects of exposure to superoxide radicals are counteracted by the activity of superoxide dismutase (SOD). We have shown previously that Campylobacter coli possesses an iron cofactored SOD. The sodB gene of C. coli UA585 was insertionally inactivated by the site-specific insertion of a tetO cassette. Organisms harboring the inactivated gene failed to produce a biologically functional form of the enzyme. While the ability of this mutant to grow in aerobic conditions was unchanged relative to the parental strain, its survival was severely compromised when nongrowing cells were exposed to air. Accordingly, the SOD-deficient mutant was unable to survive for prolonged periods in model foods. Furthermore, inactivation of the sodB gene decreased the colonization potential in an experimental infection of 1-day-old chicks. In contrast, strain CK100, which is deficient in catalase activity, showed the same survival and colonization characteristics as the parental strain. These results indicate that SOD, but not catalase, is an important determinant in the ability of C. coli to survive aerobically and for optimal colonization within the chicken gut.     

A systematic approach to evaluate the modification of lens proteins by glycation-induced crosslinking

To systematically evaluate the modification of lens proteins by aldose and dicarbonyl sugars during the glycation process, the sugar-dependent incorporation of Lys and Arg, SDS–PAGE profile, amino acid analysis, and fluorophore formation (excitation 370 nm/emission 440 nm) were determined. Reaction mixtures with glycolaldehyde, glyceraldehyde, threose and 3-deoxythreosone showed the greatest extent of Lys crosslinking and fluorescence formation. An increase in fluorescence intensity, but a decrease in Lys and Arg crosslinking, was found with glyoxal, methylglyoxal, hydroxypyruvaldehyde and threosone. In addition glyoxal, methylglyoxal and hydroxypyruvaldehyde caused the specific loss of Arg residues in lens proteins. Reaction mixtures with xylose, xylosone, glucose, glucosone and 3-deoxyglucosone exhibited the least protein modifications; however, incubation with 3-deoxyxylosone resulted in extensive loss of Lys and Arg residues, a higher extent of Lys or Arg crosslinking and significant fluorophore formation. Each sugar exhibited unique characteristics in the modification of lens proteins by glycation. To validly compare the protein modifications occurring during glycation reactions, a systematic approach was employed to evaluate the potential role of aldose and dicarbonyl sugars in protein modification.     

Superoxide sensitivity of the Escherichia coli aconitase.

Mutants of Escherichia coli lacking superoxide dismutase (SOD) activity were used to explore the sensitivity of aconitase toward O2 and O2-. The aconitase activity in SOD-free extracts was rapidly lost under aerobic conditions and exogenous SOD afforded a concentration-dependent protection. The rate of the inactivating reaction between O2- and aconitase was estimated to be of the order of 10(9) M-1 s-1. The competitive inhibitors fluorocitrate and tricarballylate provided some protection, and at saturating concentrations, they decreased the rate of the inactivating reaction by 100- and 10-fold, respectively. Aconitase was markedly less sensitive to O2 than it was to O2-. Aerobic growth on succinate involves a greater dependence upon aconitase than does growth on glucose and, as expected, the deleterious consequences of SOD deficiency were more pronounced on succinate than on glucose. Moreover, aconitase activity was lower in extracts of aerobically grown SOD mutants, than it was in the parental strain. We suppose that inactivation of aconitase by O2- involves oxidative attack on the prosthetic iron-sulfur cluster. The extreme sensitivity of aconitase to inactivation by O2- suggests that its inactivation will be an early event in the oxidative stress imposed by hyperoxia, ultraviolet irradiation or redox-cycling agents, such as viologens or quinones.     

Role of rpoS in the regulation of glyoxalase III in Escherichia coli

Methylglyoxal is an endogenous electrophile produced in Escherichia coli by the enzyme methylglyoxal synthase to limit the accumulation of phosphorylated sugars. In enteric bacteria methylglyoxal is detoxified by the glutathione-dependent glyoxalase I/II system, by glyoxalase III, and by aldehyde reductase and alcohol dehydrogenase. Here we demonstrate that glyoxalase III is a stationary-phase enzyme. Its activity reached a maximum at the entry into the stationary phase and remained high for at least 20 h. An rpoS- mutant displayed normal glyoxalase I and II activities but was unable to induce glyoxalase III in stationary phase. It thus appears that glyoxalase III is regulated by rpoS and might be important for survival of non-growing E. coli cultures.     

Generation of a superoxide dismutase (SOD)-deficient mutant of Campylobacter coli: evidence for the significance of SOD in Campylobacter survival and colonization.

The microaerophilic nature of Campylobacter species implies an inherent sensitivity towards oxygen and its reduction products, particularly the superoxide anion. The deleterious effects of exposure to superoxide radicals are counteracted by the activity of superoxide dismutase (SOD). We have shown previously that Campylobacter coli possesses an iron cofactored SOD. The sodB gene of C. coli UA585 was insertionally inactivated by the site-specific insertion of a tetO cassette. Organisms harboring the inactivated gene failed to produce a biologically functional form of the enzyme. While the ability of this mutant to grow in aerobic conditions was unchanged relative to the parental strain, its survival was severely compromised when nongrowing cells were exposed to air. Accordingly, the SOD-deficient mutant was unable to survive for prolonged periods in model foods. Furthermore, inactivation of the sodB gene decreased the colonization potential in an experimental infection of 1-day-old chicks. In contrast, strain CK100, which is deficient in catalase activity, showed the same survival and colonization characteristics as the parental strain. These results indicate that SOD, but not catalase, is an important determinant in the ability of C. coli to survive aerobically and for optimal colonization within the chicken gut.     

Sterols and Triterpenoids from the Fruit of Cydonia oblonga Miller

An enzymatic method for glycolaldehyde production from ethylene glycol was investigated using immobilized alcohol oxidase and catalase. Those enzymes were immobilized onto Chitopearl BCW 3501. When only alcohol oxidase was immobilized onto it, the apparent activity was 190 units/g in wet gel using methanol as the substrate. Tris-HCl buffer (1.5 M; pH 9.0) was selected based on a high stability of glycolaldehyde and a low production of glyoxal as a by-product. Under the optimum conditions, 0.97 M glycolaldehyde was formed from 1.0 M ethylene glycol and the ratio of glyoxal to glycolaldehyde was less than 1%.     

Chlorate Reducing Activity of Spinach Nitrate Reductase

The activities of 2-oxoaldehyde-metabolizing enzymes (glyoxalase I, glyoxalase II, methyl- glyoxal reductase, methylglyoxal dehydrogenase and lactaldehyde dehydrogenase) were found to be widely distributed among microorganisms. One of the enzymes, methylglyoxal reductase, which catalyzes the reductive conversion of methylglyoxal into lactaldehyde, was purified from Escherichia coli cells. The enzyme was judged to be homogeneous on polyacrylamide gel electrophoresis and was a monomer with a molecular weight of 43000. The enzyme was most active at pH 6.5 and 45°C. The enzyme utilized both NADPH and NADH for the reduction of 2- oxoaldehydes (glyoxal, methylglyoxal, phenylglyoxal and 4,5-dioxovalerate) and some aldehydes (glycolaldehyde, D,l-glyceraldehyde, propionaldehyde and acetaldehyde). The Km values of the enzyme for methylglyoxal, NADPH and NADH were 4.0 mm, 1.7 fiM and 2.8 /¿m, respectively. The product of methylglyoxal reduction was identified as lactaldehyde. The enzyme from E. coli cells was different from the yeast and goat liver enzymes in both molecular structure and substrate specificity.     

The Sugar Model: Catalysis by Amines and Amino Acid Products

Ammonia and amines (including amino acids) were shown tocatalyze the formation of sugars from formaldehyde andglycolaldehyde, and the subsequent conversion of sugars tocarbonyl-containing products under the conditions studied (pH5.5 and 50°C). Sterically unhindered primary amineswere better catalysts than ammonia, secondary amines, andsterically hindered primary amines (i.e.-aminoisobutyric acid). Reactions catalyzed by primaryamines initially consumed formaldehyde and glycolaldehyde about15–20 times faster than an uncatalyzed control reaction. Theamine-catalyzed reactions yielded aldotriose (glyceraldehyde),ketotriose (dihydroxyacetone), aldotetroses (erythrose andthreose), ketotetrose (erythrulose), pyruvaldehyde, acetaldehyde,glyoxal, pyruvate, glyoxylate, and several unindentifiedcarbonyl products. The concentrations of the carbonyl products,except pyruvate and ketotetrose, initially increased and thendeclined during the reaction, indicating their ultimateconversion to other products (like larger sugars or pyruvate).The uncatalyzed control reaction yielded no pyruvate orglyoxylate, and only trace amounts of pyruvaldehyde, acetaldehyde and glyoxal. In the presence of 15 mM catalyticprimary amine, such as alanine, the rates of triose andpyruvaldehyde of synthesis were about 15-times and 1200-timesfaster, respectively, than the uncatalyzed reaction. Sinceprevious studies established that alanine is synthesized fromglycolaldehyde and formaldehyde via pyruvaldehyde as its directprecursor, the demonstration that the alanine catalyzes theconversion of glycolaldehyde and formaldehyde to pyruvaldehydeindicates that this synthetic pathway is capable ofautocatalysis. The relevance of this synthetic process, namedthe Sugar Model, to the origin of life is discussed.     

Expression of a familial amyotrophic lateral sclerosis-associated mutant human superoxide dismutase in yeast leads to decreased mitochondrial electron transport

Strains of Saccharomyces cerevisiae that express either the wild type or the amyotrophic lateral sclerosis-associated mutant human copper-zinc superoxide dismutase (SOD1) proteins A4V and G93A, respectively, in a yeast SOD1-deficient parent strain were used to investigate the hypothesis that expression of a mutant SOD1 protein causes deficient mitochondrial electron transport as a possible mechanism for disease induction. Mitochondria isolated from the wild type SOD1-expressing yeast were identical to mitochondria from the parent strain in heme content and activities of complexes II, III, and IV. Mitochondria isolated from the A4V-expressing yeast had decreased rates of electron transport in complexes II+III, III, and IV and corresponding decreases in hemes b, c-c1, and a-a3 content compared to mitochondria from wild type human SOD1-expressing yeast. Mitochondria isolated from G93A-expressing yeast had decreased rates of electron transport in complex IV and probably in complex II with a corresponding decrease in heme a-a3 content. These results suggest that mutant SOD1-expression causes defective electron transport complex assembly and that the yeast system will provide an excellent model for the study of the mechanism of mutant SOD1-induced mitochondrial electron transport defects.     

Protective role of mitochondrial superoxide dismutase against high osmolarity,heat and metalloid stress in<Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis>

Superoxide dismutases, both cytosolic Cu, Zn-SOD encoded by SOD1 and mitochondrial Mn-SOD encoded by SOD2, serve Saccharomyces cerevisiae cells for defense against the superoxide radical but the phenotypes of sod1A and sod2delta mutant strains are different. Compared with the parent strain and the sod1delta mutant, the sod2delta mutant shows a much more severe growth defect at elevated salt concentrations, which is partially rescued by 2 mmol/L glutathione. The growth of all three strains is reduced at 37 degrees C, the sod2delta showing the highest sensitivity, especially when cultured in air. Addition of 1 mmol/L glutathione to the medium restores aerobic growth of the sod1delta mutant but has only a minor effect on the growth of the sod2delta strain at 37 degrees C. The sod2delta strain is also sensitive to AsIIl and AsV and its sensitivity is much more pronounced under aerobic conditions. These results suggest that, unlike the Sodlp protein, whose major role is oxidative stress defense, Sod2p also plays a role in protecting S. cerevisiae cells against other stresses--high osmolarity, heat and metalloid stress.     

Superoxide sensitivity of the Escherichia coli 6-phosphogluconate dehydratase.

The activity of 6-phosphogluconate dehydratase was significantly lower in extracts of aerobically grown Escherichia coli deficient in superoxide dismutase (sodAsodB) and in mutants lacking the inducible manganese-containing superoxide dismutase (sodA), exposed to the redox-cycling agent paraquat, than in the parental strain. Growth of these strains on a gluconate minimal medium was also impaired under these conditions. The enzyme was most susceptible to dioxygen in superoxide dismutase (SOD)-free extracts, and exogenous SOD afforded a concentration-dependent protection against inactivation. The amount of SOD necessary for full protection was comparable to the amount normally present in extracts of aerobic E. coli (7-36 units/mg protein), and the rate of reaction of O2- with the dehydratase was estimated to be approximately 2.0 x 10(8) M-1 s-1. The dehydratase was much less sensitive to O2 or H2O2 than to O2-. The virtual substrate, alpha-glycerophosphate, provided partial protection. Iron chelators, thiol-reactive reagents, and oxidants, including nitrite and diamide, inactivated the enzyme. Fluoride ions stabilized the dehydratase and blocked the effect of oxidants. The O2(-)-sensitive target site is proposed to be an iron-sulfur cluster which is readily destroyed by oxidation.     

Expression of human FALS SOD in motorneurons of Drosophila.

Mutations in human CuZn superoxide dismutase (SOD) have been associated with familial amyotrophic lateral sclerosis (FALS). Although leading to many experimental advances, this finding has not yet led to a clear understanding of the biochemical mechanism by which mutations in SOD promote the degeneration of motorneurons that causes this incurable paralytic disease. To explore the biochemical mechanism of FALS SOD-mediated neuropathogenesis, we used transgenic methodology to target the expression of a human FALS SOD to motorneurons of Drosophila, an organism known for its phenotypic sensitivity to genetic manipulation of SOD. Earlier, we showed that targeted expression of human SOD in motorneurons of Drosophila causes a dramatic extension of adult lifespan (>40%) and rescues most of the phenotypes of SOD-null mutants. Using the same genetic system, we now ask if targeted expression of a mutant allele of human SOD that is associated with FALS causes paralysis and premature death, or is otherwise injurious in Drosophila as it is in humans and transgenic mice. Here we report that high-level expression of a human FALS SOD in motorneurons is not detrimental and does not promote paralysis and premature death when expressed in motorneurons of Drosophila. In sharp contrast, the expression of FALS SOD in Drosophila actually extends lifespan, augments resistance to oxidative stress and partially rescues SOD-null mutants in a manner predicted by our earlier studies on the expression of wildtype human SOD in Drosophila motorneurons.