Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:1.6.5.3 (complex I)
8,901 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The location of ferrochelatase in bovine heart mitochondria has been studied. When the mitochondria were fractionated into Complexes I, II and III, ferrochelatase activity was only found in Complex I. Complex I also showed heme synthesis from ferric ion in the presence of NADH as an electron donor. Immunoblot experiments confirmed the presence of ferrochelatase in Complex I, but not in Complexes II or III. Some phospholipids, including phosphatidylserine and cardiolipin, stimulated NADH-dependent heme synthesis from ferric ion. When purified ferrochelatase was incubated with the low molecular weight form of NADH dehydrogenase prepared from Complex I, heme synthesis from ferric ion occurred by the addition of NADH. FMN markedly elevated the synthesis. These results indicate that ferrous ion is produced by NADH oxidation in Complex I and is then utilized for heme synthesis by ferrochelatase.
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PMID:Association of ferrochelatase with Complex I in bovine heart mitochondria. 309 Oct 80

We examined the activity of heme synthesis when ferrochelatase purified from rat liver mitochondria was incubated with ferric chloride and mesoporphyrin IX as substrates in the absence of reducing reagents. In the presence of the NADH dehydrogenase-rich fraction and NAD(P)H, mesoheme was synthesized; the addition of FMN or FAD markedly enhanced the activity. These results indicate that the NAD(P) H-oxidizing system reduces ferric ion to ferrous ion. This ferrous ion is then utilized for heme synthesis by ferrochelatase. The effect of lead on NAD(P)H-dependent heme synthesis was also examined. Lead reduced NAD(P)H-dependent heme synthesis by 50% at 10(-5) M, but had no effect when ferrous ion was used as substrate. Zn-Porphyrin synthesis was not changed in the presence of Pb2+ at 10(-5) M. Thus, heme synthesis from ferric ion was more susceptible to Pb2+ than heme synthesis from ferrous ion.
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PMID:Reconstitution of heme-synthesizing activity from ferric ion and porphyrins, and the effect of lead on the activity. 393 55

Sonicated mitochondria catalyse the reduction of ferric salts, and the subsequent incorporation of Fe(2+) into haem, when provided with a reducing substrate such as succinate or NADH. The rate of haem synthesis was low under aerobic conditions and, after a short lag period, accelerated once anaerobic conditions were achieved; it was insensitive to antimycin A. The lag period was decreased by preincubating the mitochondria with NADH and Fe(3+). Newly formed Fe(2+) was autoxidized rapidly and the consequent O(2) uptake was measured with an oxygen electrode to determine the rate of enzymic formation of Fe(2+) from FeCl(3); this reaction was rapid in sonicated mitochondria provided with NADH or succinate and was insensitive to antimycin A. The reaction was very slow in intact mitochondria, suggesting a permeability barrier to Fe(3+) ions. This system was used to test the permeability of the mitochondrial membrane to various iron complexes of biological importance. Of the compounds tested only ferrioxamine G appeared to penetrate readily and the iron of this complex was reduced when intact mitochondria were supplied with succinate or NADH-linked substrates. The reduction was insensitive to rotenone or antimycin A. Both ferrioxamine G and ferrioxamine B were, however, reduced by particles. The membrane fraction of sonicated mitochondria was necessary for the reduction. The rate of ferrioxamine B reduction by sonicated mitochondria was measured by a dual-wavelength spectrophotometric assay and was found to be stimulated in conditions where the Fe(2+) produced was utilized for haem synthesis. The addition of FeCl(3) to anaerobic particles caused an oxidation of cytochrome b when this region of the respiratory chain was isolated by treatment with rotenone and antimycin A. These results suggest that the reduction of ferric iron and its complexes occurs inside the inner mitochondrial membrane in proximity to ferrochelatase. Possible sites for this reduction are the flavoproteins, succinate and NADH dehydrogenase.
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PMID:The utilization of iron and its complexes by mammalian mitochondria. 434 50

Heme molecules play important roles in electron transfer by redox proteins such as cytochromes. In addition, a structural role for heme in protein folding and the assembly of enzymes has been suggested. Previous results obtained using Escherichia coli hemA mutants, which are unable to synthesize 5-aminolevulinic acid, a precursor of porphyrins and hemes, have demonstrated a requirement for heme biosynthesis in the assembly of a functional succinate-ubiquinone reductase (SQR or complex II), which is a component of the aerobic respiratory chain. In the present study, in order to investigate the role of the heme in the assembly of E. coli SQR, we used a hemH (encodes ferrochelatase) mutant that lacks the ability to insert iron into the porphyrin ring. The hemH mutant failed to insert functional SQR into the cytoplasmic membrane, and the catalytic portion of SQR [the flavoprotein subunit (Fp) and the iron-sulfur protein subunit (Ip)] was localized in the cytoplasm of the cell. It is of interest to note that protoporphyrin IX accumulated in the mutant cells and inactivated the cytoplasmic succinate dehydrogenase (SDH) activity associated with the catalytic Fp-Ip complex. In contrast, SQR was assembled into the membrane of a heme-permeable hemH double mutant when hemin was present in the culture. Only a low level of SQR activity was found in the membrane when hemin was replaced by non-iron metalloporphyrins: Mn-, Co-, Ni-, Zn- and Cu-protoporphyrin IX, or protoporphyrin IX These results indicate that heme iron is indispensable for the functional assembly of SQR in the cytoplasmic membrane of E. coli, and provide a new insight into the biological role of heme in the molecular assembly of the multi-subunit enzyme complex.
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PMID:Abortive assembly of succinate-ubiquinone reductase (complex II) in a ferrochelatase-deficient mutant of Escherichia coli. 1140 22

Application of delta-aminolevulinic acid (ALA) results in the endogenous accumulation of protoporphyrin IX and is a useful approach in the photodynamic therapy (PDT) of cancers. To investigate the role of nitric oxide (NO) in the specific accumulation of protoporphyrin and ALA-induced PDT of cancerous cells, we transfected inducible-nitric oxide synthase (NOS2) cDNA into human embryonic kidney (HEK) 293T cells and examined the ALA-induced photo-damage as well as the accumulation of porphyrin in the cells. When the NOS2-expressing HEK293T cells were treated with ALA and then exposed to visible light, they became more sensitive to the light with accumulating porphyrins, as compared with the ALA-treated control cells. An increase in the generation of NO in transfected cells led to the accumulation of protoporphyrin with a concomitant decrease of ferrochelatase, the final step enzyme of heme biosynthesis. When mouse macrophage-like RAW264.7 cells were cultured with lipopolysaccharide and interferon-gamma, the expression of NOS2 was induced. The addition of ALA to these cells led to the accumulation of protoporphyrin and cell death upon exposure to light. The treatment of cells with an NOS inhibitor, NG-monomethyl-L-arginine acetate, resulted in the inhibition of protoporphyrin accumulation and cell death. The levels of mitochondrial ferrochelatase and rotenone-sensitive NADH dehydrogenase in the NOS2-induced cells decreased. These results indicated that the generation of NO augments the ALA-induced accumulation of protoporphyrin IX and subsequent photo-damage in cancerous cells by decreasing the levels of mitochondrial iron-containing enzymes. Based on the fact that the production of NO in cancerous cells is elevated, NO in the cells is responsible for susceptibility with ALA-induced PDT.
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PMID:The role of nitric oxide in delta-aminolevulinic acid (ALA)-induced photosensitivity of cancerous cells. 1719 60

Members of the bacterial and mitochondrial iron-sulfur cluster (ISC) assembly machinery include the so-called A-type ISC proteins, which support the assembly of a subset of Fe/S apoproteins. The human genome encodes two A-type proteins, termed ISCA1 and ISCA2, which are related to Saccharomyces cerevisiae Isa1 and Isa2, respectively. An additional protein, Iba57, physically interacts with Isa1 and Isa2 in yeast. To test the cellular role of human ISCA1, ISCA2, and IBA57, HeLa cells were depleted for any of these proteins by RNA interference technology. Depleted cells contained massively swollen and enlarged mitochondria that were virtually devoid of cristae membranes, demonstrating the importance of these proteins for mitochondrial biogenesis. The activities of mitochondrial [4Fe-4S] proteins, including aconitase, respiratory complex I, and lipoic acid synthase, were diminished following depletion of the three proteins. In contrast, the mitochondrial [2Fe-2S] enzyme ferrochelatase and cellular heme content were unaffected. We further provide evidence against a localization and direct Fe/S protein maturation function of ISCA1 and ISCA2 in the cytosol. Taken together, our data suggest that ISCA1, ISCA2, and IBA57 are specifically involved in the maturation of mitochondrial [4Fe-4S] proteins functioning late in the ISC assembly pathway.
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PMID:The human mitochondrial ISCA1, ISCA2, and IBA57 proteins are required for [4Fe-4S] protein maturation. 2232 89

Within-litter uniformity in pigs is a major factor affecting piglet survival and growth performance. We know that Meishan (MS) gilts have higher piglet survival rate than Large White (LW) gilts because their foetal weight is less varied. To understand the molecular basis for placental nutritional transport during the late stages of gestation in LW and MS, we employed the isobaric tags for relative and absolute quantification (iTRAQ) method to investigate alterations in the placental proteomes of LW and MS gilts on gestational day 90. Investigation of foetal weight at different uterine positions revealed that the foetal and placental weights as well as the foetal concentration of glucose were significantly higher in LW gilts positioned towards the utero-tubal junction than in those positioned toward the cervix; however, no such differences were observed in MS gilts, and MS gilts had a greater uniformity in foetal weight on day 90 of gestation. Comparisons of the proteomes between placentas positioned toward the cervix and those positioned toward the utero-tubal junction identified 38 differentially expressed proteins in the two breeds. These proteins play a central role in nutrient transport and metabolism, as well as in transcriptional and translational regulation. Of particular interest is the finding that the placentas of LW gilts showed 14 differential expression of proteins mainly related to lipid transport and energy metabolism (including solute carrier family 27, mitochondrial trifunctional protein, and NADH dehydrogenase [ubiquinone] flavoprotein 2), but only 2 proteins in MS gilts. In contrast, the differentially expressed proteins in MS gilts were primarily involved in transcriptional and translational regulation (such as ribosome-sec61 and 40S ribosomal protein S23), with a few related to glucose and coenzyme transport and metabolism (including glucose transport protein and ferrochelatase). Our results revealed that placental lipid and energy metabolism might play a crucial role in the regulation of foetal weight, based on uterine position in two distinct pig breeds. These findings provide a deeper understanding of placental efficiency that can be utilized to provide a new method to enhance the efficiency of livestock production.
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PMID:Detection of Placental Proteomes at Different Uterine Positions in Large White and Meishan Gilts on Gestational Day 90. 2793 87

Non-syndromic microcytic congenital sideroblastic anemia (cSA) is predominantly caused by defective genes encoding for either ALAS2, the first enzyme of heme biosynthesis pathway or SLC25A38, the mitochondrial importer of glycine, an ALAS2 substrate. Herein we explored a new case of cSA with two mutations in GLRX5, a gene for which only two patients have been reported so far. The patient was a young female with biallelic compound heterozygous mutations in GLRX5 (p.Cys67Tyr and p.Met128Lys). Three-D structure analysis confirmed the involvement of Cys67 in the coordination of the [2Fe2S] cluster and suggested a potential role of Met128 in partner interactions. The protein-level of ferrochelatase, the terminal-enzyme of heme process, was increased both in patient-derived lymphoblastoid and CD34+ cells, however, its activity was drastically decreased. The activity of ALAS2 was found altered and possibly related to a defect in the biogenesis of its co-substrate, the succinyl-CoA. Thus, the patient exhibits both a very low ferrochelatase activity without any accumulation of porphyrins precursors in contrast to what is reported in erythropoietic protoporphyria with solely impaired ferrochelatase activity. A significant oxidative stress was evidenced by decreased reduced glutathione and aconitase activity, and increased MnSOD protein expression. This oxidative stress depleted and damaged mtDNA, decreased complex I and IV activities and depleted ATP content. Collectively, our study demonstrates the key role of GLRX5 in modulating ALAS2 and ferrochelatase activities and in maintaining mitochondrial function.
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PMID:GLRX5 mutations impair heme biosynthetic enzymes ALA synthase 2 and ferrochelatase in Human congenital sideroblastic anemia. 3066 Mar 87

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