绿豆线粒体呼吸链在不同电子传递途径中的电子漏

绿豆线粒体的呼喊链在氧化不同义莪时有不同的呼吸速率和电子漏速率,但是Ｏ２＾－／Ｏ２比值较稳定。呼吸链部位Ⅱ的抑制剂抗霉素Ａ对α－酮茂二酸、琥珀酸及苹果本工物时的电子漏速率和Ｏ２＾－／Ｏ２比值都明显的促进作用,说明电子漏发生的位点可能在抗纱Ａ的抑制点之前。呼吸链在氧化外源ＮＡＤＨ时,线料体所产生的地氰化物、鱼藤酮、抗弱Ａ及ＳＨＡＭ都不敏感,而对钙离子的螯合剂ＥＧＴＡ显著敏感。因此,依赖于钙离子的ＮＡ     

Superoxide dismutase 1 modulates expression of transferrin receptor

Copper–zinc superoxide dismutase (SOD1) plays a protective role against the toxicity of superoxide, and studies in Saccharomyces cerevisiae and in Drosophila have suggested an additional role for SOD1 in iron metabolism. We have studied the effect of the modulation of SOD1 levels on iron metabolism in a cultured human glial cell line and in a mouse motoneuronal cell line. We observed that levels of the transferrin receptor and the iron regulatory protein 1 were modulated in response to altered intracellular levels of superoxide dismutase activity, carried either by wild-type SOD1 or by an SOD-active amyotrophic lateral sclerosis (ALS) mutant enzyme, G93A-SOD1, but not by a superoxide dismutase inactive ALS mutant, H46R-SOD1. Ferritin expression was also increased by wild-type SOD1 overexpression, but not by mutant SOD1s. We propose that changes in superoxide levels due to alteration of SOD1 activity affect iron metabolism in glial and neuronal cells from higher eukaryotes and that this may be relevant to diseases of the nervous system.     

Comparative Studies on a Superoxide Dismutase Exhibiting Enzymatic Activity with Iron and Manganese as Active Cofactor

The SOD of Propionibacterium freudenreichii, ssp. shermanii belongs to a new group of SOD'S capable of retaining activity with either Fe or Mn as active metal cofactor.

Both enzymes exhibit identical secondary structure and immunological determinants. Hydrogen peroxide irreversibly inhibits both enzymes. The protein moiety of the Fe-and Mn-SOD could be digested with trypsin to a single active fragment.     

Chronic In Vivo Sodium Azide Infusion Induces Selective and Stable Inhibition of Cytochrome c Oxidase

Abstract: The effect of chronic subcutaneous infusion of sodium azide on the activity of mitochondrial respiratory chain enzymes was investigated in Sprague-Dawley rats. Treatment with ∼1 mg/kg/h sodium azide induced chronic, partial inhibition of cytochrome c oxidase, whereas the activities of respiratory complexes I and III were not significantly affected. The inhibition of cytochrome c oxidase was evident by 7 days after infusion began, and the effect was stable for at least 3 weeks. The selectivity of azide for cytochrome c oxidase is discussed in the context of other findings of azide effects on enzymes. The results of the present study indicate that the sodium azide infusion paradigm described here provides a useful tool for the evaluation of selective and stable cytochrome oxidase inhibition in vivo.     

Mitochondrial superoxide production and respiratory activity: Biphasic response to ischemic duration

Long bouts of ischemia are associated with electron transport chain deficits and increases in free radical production. In contrast, little is known regarding the effect of brief ischemia on mitochondrial function and free radical production. This study was undertaken to examine the relationship between the duration of ischemia, effects upon electron transport chain activities, and the mitochondrial production of free radicals. Rat hearts were subjected to increasing ischemic durations, mitochondria were isolated, and superoxide production and electron transport chain activities were measured. Results indicate that even brief ischemic durations induced a significant increase in superoxide production. This rate was maintained with ischemic durations less than 15 min, and then increased further with longer ischemic times. Mechanistically, brief ischemia was accompanied by an increase in NADH oxidase activity, reflected by a specific increase in complex IV activity. In contrast, longer ischemic durations were accompanied by a decrease in NADH oxidase activity, reflected by deficits in complexes I and IV activities.     

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.     

超氧物歧化酶(SOD)在大豆下胚轴线粒体内的定位

本文介绍一种简单有效的制备、分离植物线粒体分部的方法,根据这一方法证明了大豆下胚轴线粒体内的 SOD 主要在基质可溶性部分,是属于对氰化物不敏感的 Mn-SOD,它占线粒体 SOD 总活性的80%,其余 SOD 活性主要在线粒体的膜间空间,约占总活性的16%。结果表明,SOD 在植物线粒体内的分布和定位与动物组织相似。     

AtMTM1, a novel mitochondrial protein,may be involved in activation of the manganese-containing superoxide dismutase in <Emphasis Type="Italic">Arabidopsis</Emphasis>

Mtm1p is essential for the posttranslational activation of manganese-containing superoxide dismutase (SOD2) in Saccharomyces cerevisiae; however, whether the same holds true for Arabidopsis thaliana is unknown. In this study, by using the yeast mtm1 mutant complementation method, we identified a putative MTM gene (AtMTM1, At4g27940) that is necessary for SOD2 activation. Further, analysis of SOD activity revealed that an SOD2 defect is rescued in the yeast mutant Y07288 harboring the AtMTM1 gene. Related mRNA-level analysis showed the AtMTM1 gene is induced by paraquat but not by hydrogen peroxide, which indicates that this gene is related to the superoxide scavenger SOD. In addition, an AtMTM1::GFP fusion construct was transiently expressed in the protoplasts, and it was localized to the mitochondria. Furthermore, sequence deletion analysis of AtMTM1 revealed that the code region (amino acid (aa) 60–198) of Mtm1p plays an important role in localization of the protein to the mitochondria. Regulation of AtMTM1 gene expression was analyzed using a fusion construct of the 1,766 bp AtMTM1 promoter and the GUS (β-glucuronidase) reporter gene. The screen identified GUS reporter gene expression in the developing cotyledons, leaves, roots, stems, and flowers but not in the siliques. Our results suggest that AtMTM1 encodes a mitochondrial protein that may be playing an important role in activation of MnSOD1 in Arabidopsis.     

The Positive Charge at Position 189 IS Essential for the Catalytic Activity of Iron-and Manganese-Containing Superoxide Dismutases

We have previously shown (C.L. Borders, Jr. el al., (1989) Archives of Biochemistry and Eiaphysics. 268, 74–80) that the iron-containing (FeSOD) and manganese-containing (MnSOD) superoxide dismutases from Eschericliia coli are extensively (≥98%) inactivated by treatment with phenylglyoxal. an arginine-specific reagent. Examination of the published primary sequences of these two enzymes shows that Arg-189 is the only conserved arginine. This arginine is also conserved in the three additional FeSODs and seven of the eight additional MnSODs sequenced to date, with the only exception king the MnSOD from Saccharomyces cerevisiae, in which it is conservatively replaced by lysine. Treatment of S. cerevisiae MnSOD with phenylglyoxal under the same conditions used for the E. coli enzymes gives very little inactivation. However, treatment with low levels of 2.4.6-trinitrobenzenesulfonate (TNBS) and acetic anhydride, two lysine-selective reagents that cause a maximum of 65–80% inactivation of the E. coli SODs, gives complete inactivation of the yeast enzyme. Total inactivation of yeast MnSOD with TNBS correlates with the modification of approximately 5 lysines per subunit, whereas 6–7 lysines per subunit are acylated with acetic anhydride on complete inactivation. It appears that the positive charge contributed by residue 189. lysine in yeast MnSOD and arginine in all other SODs. may be critical for the catalytic activity or MnSODs and FeSODs.     

Glutathione precursors replenish decreased glutathione pool in cystinotic cell lines

Cystinosis is an inherited disorder due to mutations in the CTNS gene which encodes cystinosin, a lysosomal transmembrane protein involved in cystine export to the cytosol. Both accumulation of cystine in the lysosome and decreased cystine in the cytosol may participate in the pathogenic mechanism underlying the disease. We observed that cystinotic cell lines have moderate decrease of glutathione content during exponential growth phase. This resulted in increased solicitation of oxidative defences of the cell denoted by concurrent superoxide dismutase induction, although without major oxidative insult under our experimental conditions. Finally, decreased glutathione content in cystinotic cell lines could be counterbalanced by a series of exogenous precursors of cysteine, denoting that lysosomal cystine export is a natural source of cellular cysteine in the studied cell lines.     

A Selective Increase in Particulate Superoxide Dismutase Activity in Parkinsonian Substantia Nigra

The total activity of superoxide dismutase (SOD) and cytosolic and particulate activity of SOD in human substantia nigra and cerebellum were measured by a spectrophotometric method based on the ability of SOD to inhibit the autoxidation of adrenaline. The cytosolic and particulate isoenzymes of SOD were differentiated by the inclusion of potassium cyanide which selectively inhibits cytosolic copper/zinc-dependent SOD activity. In autopsied human brains, there was no difference in total SOD activity, or the activity of SOD in cytosol in substantia nigra of patients dying with Parkinson's disease compared to age-matched controls. However, the activity of the particulate form of SOD was higher in the parkinsonian substantia nigra compared to control tissue. In the cerebellum there was no difference in the total, cytosolic, or particulate activity of SOD between parkinsonian patients and age-matched controls. Increased activity of SOD in particulate fraction may be a protective response to elevated levels of toxic free radicals in the parkinsonian substantia nigra. Alternatively, increased SOD activity may induce cell death through the accumulation of hydrogen peroxide.     

Daily rhythm of MnSOD in the C<Subscript>3</Subscript>-CAM intermediate <Emphasis Type=Italic>Clusia fluminensis</Emphasis> Planch. et Triana.

The C₃-CAM intermediate plant Clusia fluminensis under well-watered at low light conditions opens stomata during the light period. In leaf extracts of this plant we have found two copper-zinc superoxide dismutases (CuZnSODs) and two manganese SODs: MnSOD-like protein (MnSOD II) and MnSOD I. Daily rhythm of the MnSOD I shows maximum activity during the afternoon hours and it is accompanied by only a very small tendency to increase in catalase (CAT) activity and lowering of citrate level.