Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “OXYGENASES”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 523 records · Page 29Linked to original sources
PubMed2003

Purification, characterization and functional cloning of inositol oxygenase from Cryptococcus.

The enzyme inositol oxygenase (myo-inositol : oxygen oxidoreductase; E.C. 1.13.99.1) is a monooxygenase that converts inositol into glucuronic acid in the presence of molecular oxygen. This enzyme is integrated into a pathway leading to either degradation and energy production or the biosynthesis of precursors for polysaccharides. The enzyme was purified from the yeast Cryptococcus lactativorus by a five-step chromatography procedure. The purified enzyme shows a molecular mass of 37 kDa on SDS-PAGE, similar to the estimation of the size of the native enzyme determined by size exclusion chromatography. Peptides of the inositol oxygenase protein derived from a tryptic digest were sequenced de novo by nanoelectrospray tandem mass spectrometry. Using degenerate oligonucleotides, the corresponding gene was cloned from first strand cDNA. The open reading frame encodes a 315 amino acid polypeptide with a predicted molecular mass of 36.9 kDa. Inositol oxygenase is a single copy gene in C. lactativorus. It has close homologues in other fungi such as Cryptococcus neoformans and Neurospora crassa. Biochemical characterization of the enzyme showed a pH optimum of 6-6.5 and a temperature optimum of 30 degrees C. Myo-inositol is the only accepted substrate with a Km of ca. 5 mM. The enzyme contains a Fe-centre but the enzyme activity is resistant to KCN.

Amino Acid Sequence↗
PubMed1998

Heme oxygenase in the experimental ALS mouse.

Heme oxygenase-1 (HO-1) is a stress protein inducible in some cells by oxidative stress. The status of heme oxygenase was investigated in a transgenic mouse model of amyotrophic lateral sclerosis (ALS) since oxidative mechanisms are postulated in neuronal injury. Three ALS mice [(SOD1-G93A)1Gur] and three controls [(SOD-1)2Gur] were obtained from The Jackson Laboratory. Behavioral differences suggestive of neurodegeneration in ALS mice developed at 4-5 months of age. All mice were killed at 7-8 months of age. Tissue vacuolation, cell loss, and the presence of GFAP+ cells were noted in the spinal cords of ALS mice. Spinal cord motor neurons in both control and ALS mice stained positive for heme oxygenase-2 (HO-2). While not precluding the presence of low levels of HO-1 neither immunohistochemical staining nor Western blot analysis provided evidence for significant HO-1 induction in degenerating spinal cord.

Amyotrophic Lateral Sclerosis↗
PubMed1988

Tin-protoporphyrin inhibits heme oxygenase and prevents the decline in hepatic heme and cytochrome P-450 contents produced in nude mice by tumor transplantation.

Heme and hemeprotein perturbations are present in nude mice bearing transplanted tumors. Hepatic microsomal heme oxygenase activity is increased 50-100% in tumor bearing nu/nu mice when compared with normal controls. This elevation in activity of the rate-limiting enzyme of heme degradation is associated with a 50% depletion of microsomal heme and cytochrome P-45 concentrations in liver. The synthetic heme analogue, Sn-protoporphyrin, a potent inhibitor of heme oxygenase, lowers the activity of heme oxygenase in tumor bearing animals to below control levels. This effect is associated with a normalization of hepatic heme and cytochrome P-450 contents. These findings might have implications for protecting normal cells during tumor growth and chemotherapy.

Animals↗
PubMed1988

Detection of two heme oxygenase isoforms in the human testis.

This study shows heme oxygenase multiplicity is common to rat and human tissues. The isozymes in man and rat, however, are heterogenous proteins that share certain characteristics. Two forms of heme oxygenase, HO-1 and HO-2, were identified in human testis. HO-2 form was the prevalent form. Human and rat HO-1 differed in chromatographic behavior and molecular weight; human HO-1 was a larger molecule (35,400 vs 30,000). The two forms, however, were similar in that immunochemically human HO-1 exhibited reactivity toward antibody to rat HO-1. Human and rat HO-2 also were dissimilar in chromatographic behavior and showed only a weak immunological cross-reactivity. Human and rat HO-1 were essentially the same size. As in rat organs, the microsomal cytochrome P-450 content in human testis was reciprocal to heme oxygenase activity.

Animals↗
PubMed1989

Posttranslational and direct integration of heme oxygenase into microsomes.

Rat liver heme oxygenase has a large cytoplasmically exposed domain containing the N-terminus that can be cleaved from the membranes by a low concentration of trypsin, indicating that heme oxygenase is embedded in membranes with an insertion sequence near its C-terminal portion. Heme oxygenase synthesized in a cell-free system or purified from microsomes after detergent-solubilization was integrated into microsomal membranes posttranslationally and directly, like cytochrome b5.

Animals↗
PubMed1990

Activation of heme oxygenase and heat shock protein 70 genes by stress in human hepatoma cells.

Effects of various stresses were examined on the accumulation of mRNA for microsomal heme oxygenase and a heat shock protein, hsp70, in three human hepatoma cell lines. By heat shock, hsp70 mRNA was induced in all three hepatoma lines, Hep G2, Hep 3B and Hep G2f, while heme oxygenase mRNA was increased only in Hep 3B. Time-courses of the heat shock induction of both mRNAs in Hep 3B were similar. Arsenite caused induction of both mRNAs in all three cell lines, while cadmium increased them in Hep G2 and Hep 3B, but not in Hep G2f cells. These findings suggest that, although both hsp70 and heme oxygenase are heat shock proteins, the mode of induction of mRNAs for these proteins is different.

Arsenic↗
PubMed2004

Antioxidant action of L-alanine: heme oxygenase-1 and ferritin as possible mediators.

The amino acid L-alanine has been shown to exert long-term cytoprotection by as yet unidentified molecular mechanisms. Using cultured human endothelial cells (ECV 304), the present study investigates the effect of L-alanine on hydrogen peroxide-mediated cytotoxicity and expression of the antioxidant stress proteins, heme oxygenase-1 (HO-1) and ferritin. Pretreatment with L-alanine (0.3-3mM) protected endothelial cells from hydrogen peroxide-dependent cytotoxicity and increased the surviving endothelial cell fraction by 76%. The described protection was associated with a significant induction of heme oxygenase activity and ferritin protein synthesis. A protective effect similar to L-alanine was observed when preincubating the cells with iron-free apoferritin or the antioxidant HO-1 product, bilirubin. The present study demonstrates that L-alanine stimulates expression of the antioxidant defense proteins HO-1 and ferritin in endothelial cells. Increased heme oxygenase activity and ferritin expression improve endothelial dysfunction suggesting an antiatherogenic potential of L-alanine.

Alanine↗
PubMed2026

Bioprospecting microbial genomes to expand the biocatalytic toolbox of rubber oxygenases.

A set of rubber oxygenases was discovered through phylogenetic analysis and AI-based structural modeling of complexes of the putative enzymes with a substrate mimicking cis-1,4-polyisoprene. Sixteen candidate proteins were selected from thermophilic microorganisms, all sequence-related to the Latex clearing protein from Streptomyces sp. K30 (LcpK30). Sequence truncation and solubility tags were then evaluated to enhance protein expression, with the SUMO tag proving to be the most effective. Including LcpK30, nine heme-containing oxygenases were successfully expressed in E. coli NEB 10-beta cells, purified (35-157 mg L-1 yield) and characterized. Steady-state kinetics revealed significant rubber latex-degrading properties for six of them, with the truncated SUMO-fused LcpK30 (SUMO-LcpK30T) showing activity in agreement with literature. Notably, the catalytic efficiencies of all the expressed homologs lay within one order of magnitude and the oxygenase from Thermomonospora echinospora was found to be particularly promising in terms of activity, especially at high latex concentrations (more than 1% w/v). The analysis of reaction mixtures by both HPLC and HPLC-MS confirmed the oxidation of cis-1,4-polyisoprene to form the expected isoprenoid oligomers (n = 2-12), whose distribution was consistent with the usual endo-type cleavage pattern in all but one case. This bioprospecting effort afforded a platform of new rubber-degrading enzymes with diverse efficiencies and product profiles, capable of adapting to targeted applications.

Oxygenases↗
PubMed2000

Crystal structure of rat heme oxygenase-1 in complex with heme.

Heme oxygenase catalyzes the oxidative cleavage of protoheme to biliverdin, the first step of heme metabolism utilizing O(2) and NADPH. We determined the crystal structures of rat heme oxygenase-1 (HO-1)-heme and selenomethionyl HO-1-heme complexes. Heme is sandwiched between two helices with the delta-meso edge of the heme being exposed to the surface. Gly143N forms a hydrogen bond to the distal ligand of heme, OH(-). The distance between Gly143N and the ligand is shorter than that in the human HO-1-heme complex. This difference may be related to a pH-dependent change of the distal ligand of heme. Flexibility of the distal helix may control the stability of the coordination of the distal ligand to heme iron. The possible role of Gly143 in the heme oxygenase reaction is discussed.

Animals↗
PubMed2000

Age-dependent increase of heme oxygenase-1 gene expression in the liver mediated by NFkappaB.

Heme, the iron-porphyrin coordination complex, released from the degradation of hemoproteins, is a strong prooxidant. It is enzymatically degraded by heme oxygenase to free iron, carbon monoxide and biliverdin. Biliverdin and its reduced metabolite bilirubin are two potent physiological antioxidants. Here we show a progressive increase of steady-state levels of the mRNA encoding the inducible isoform of this enzyme (heme oxygenase-1) in the rat liver during aging. We had previously reported that aging is associated with increased activation of the nuclear factor kappaB (NFkappaB). We now provide evidence to establish that overexpression of NFkappaB in transfected liver-derived HepG2 cells can cause a marked induction of the endogenous heme oxygenase-1 (HO-1) mRNA and activation of the cotransfected HO-1 gene promoter. Taken together, these results support the conclusion that enhanced oxidative stress during aging is accompanied by compensatory induction of the antioxidant enzyme HO-1 through activation of the NFkappaB pathway.

Animals↗
PubMed1999

Heme oxygenase-1 expression in oral squamous cell carcinoma as involved in lymph node metastasis.

Thirty-eight oral squamous cell carcinomas (SCCs) were semi-quantitatively analyzed by immunohistochemical staining, and the relation between heme oxygenase-1 (HO-1) expression and the clinical status were correlated. High immunostaining of HO-1 was detected in lymph node metastasis negative groups (P = 0.0018) and in well-differentiated SCCs (P = 0.0016). There were no significant correlations between heme oxygenase-1 expression and other factors, such as size of the tumor, staging, age and sex. These findings further support the proposition that high heme oxygenase-1 expression in oral SCCs can be useful in identifying patients at low risk of lymph node metastasis.

Adult↗
PubMed2002

1,2,3,4,6-Penta-O-galloyl-beta-D-glucose protects rat neuronal cells (Neuro 2A) from hydrogen peroxide-mediated cell death via the induction of heme oxygenase-1.

The root of Paeonia suffruticosa ANDREWS is an important Chinese crude drug used in many traditional prescriptions. 1,2,3,4,6-Penta-O-galloyl-beta-D-glucose (PGG), a major component of this crude drug, has been shown to possess potent anti-oxidant, anti-mutagenic and anti-proliferative effects. In the present study, we examined the effect of PGG on the expression of neuronal heme oxygenase-1 (HO-1), an inducible stress protein that degrades heme to the neuroactive molecule, carbon monoxide and the anti-oxidant, biliverdin. Exposure of Neuro 2A cells to PGG (10-50 microM) resulted in a concentration- and time-dependent induction of HO-1 mRNA, and protein expressions and heme oxygenase activity. Interestingly, pretreatment of the neuronal cells with PGG resulted in enhanced cellular resistance to hydrogen peroxide. This cytoprotective effect was reversed by zinc protoporphyrin IX, an inhibitor of heme oxygenase. This study showed that PGG could protect neuronal cells from oxidative stress via the induction of HO-1 gene expression.

Animals↗
PubMed2002

Paradoxical effects of metalloporphyrins on doxorubicin-induced apoptosis: scavenging of reactive oxygen species versus induction of heme oxygenase-1.

The cytoprotective effects of redox-active metalloporphyrins (e.g., FeTBAP and MnTBAP) were generally attributed to their ability to scavenge reactive oxygen and nitrogen species. In this study, we evaluated the pro- and antiapoptotic potentials of different metalloporphyrins containing iron, cobalt, zinc, and manganese in adult rat cardiomyocytes exposed to doxorubicin (DOX), an anticancer drug that forms superoxide and hydrogen peroxide via redox-cycling of DOX semiquinone in the presence of molecular oxygen. We used electron spin resonance/spin trapping and cytochrome c reduction to assess the scavenging of superoxide anion by metalloporphyrins. Superoxide anion was effectively scavenged by FeTBAP and MnTBAP but not by CoTBAP and ZnTBAP. FeTBAP efficiently scavenged H(2)O(2). Both CoTBAP and FeTBAP inhibited DOX-induced cardiomyocyte apoptosis. These findings implicate that mechanisms other than oxy-radical scavenging may account for their antiapoptotic property. In addition, CoTBAP and FeTBAP induced heme oxygenase-1 more potently than did MnTBAP and ZnTBAP. Inhibition of heme oxygenase abolished the protective effect of CoTBAP and reduced the protection by FeTBAP against DOX-induced cardiomyocyte apoptosis. We propose that metalloporphyrins can inhibit apoptosis either by inducing heme oxygenase-1 and antiapoptotic protein signaling or by scavenging reactive oxygen species.

Animals↗
PubMed2003

Nitric oxide priming protects nitric oxide-mediated apoptosis via heme oxygenase-1 induction.

The role of nitric oxide (NO) as a cytotoxic effector molecule of the immune system is clearly established, but recent studies demonstrate cytoprotective functions of NO at low nontoxic concentrations. However, the mechanism of cytoprotection has not been defined completely. Thus, we investigate the involvement of heme oxygenase-1 (HO-1) in the cytoprotective effects of NO. Exposure of L929 cells to sodium nitroprusside (SNP) resulted in the induction of HO-1 protein expression and heme oxygenase activity. Pretreatment of the cells with a low dose of NO (200 microM SNP) significantly inhibited a high dose of (1000 microM SNP) NO-induced apoptosis in L929 cells. Cytoprotection by a low dose of NO was abrogated in the presence of the heme oxygenase inhibitor zinc protoporphyrin IX. A cytoprotective effect comparable to a low dose of SNP was observed when the cells were transfected with HO-1 gene or preincubated with another HO-1 inducer, hemin. Additional experiments revealed the involvement of carbon monoxide in the cytoprotective effect of SNP/HO-1 in L929 cells. Our results presented here provide evidence to support the essential role of HO-1 in the cytoprotective function of NO priming.

Animals↗
PubMed1981

Specificity of heme oxygenase: a study with synthetic hemins.

A large number of synthetic iron porphyrins were enzymatically oxidized by a microsomal heme oxygenase preparation from rat liver. They all had in common two vicinal propionic acid residues at C6 and C7. Iron porphyrins of type I were not substrates of the enzyme. Iron porphyrins that carried electron-withdrawing substituents (acyl residues) at C2 and C4 were substrates of heme oxygenase, although the product yields were reduced. Several iron porphyrins, such as hemin XIII (4) and hem III (5), were better substrates of heme oxygenase than the natural substrate hemin IX (1). The enzymatic oxidation was selective for the alpha-methine bridge, and the alpha-biliverdins obtained were reduced by Biliverdin reductase to the corresponding alpha-bilirubins. Preincubation of the enzymatic system with hemin IX (1) and hemin XIII (4) in the absence of NADPH resulted in an inhibition of their oxidation. The iron-free porphyrins which carried two vicinal propionic acid residues at C6 and C7 were also found to be inhibitors of the enzymatic system when preincubated with the latter. The presence of hematochemin IX (18) suppressed the enzymatic oxidation of hemin IX (1).

Animals↗
PubMed2003

Heme oxygenase-1 accelerates tumor angiogenesis of human pancreatic cancer.

Angiogenesis is necessary for the continued growth of solid tumors, invasion and metastasis. Several studies clearly showed that heme oxygenase-1 (HO-1) plays an important role in angiogenesis. In this study, we used the vital microscope system, transparent skinfold model, lung colonization model and transduced pancreatic cancer cell line (Panc-1)/human heme oxygenase-1 (hHO-1) cells, to precisely analyze, for the first time, the effect of hHO-1 gene on tumor growth, angiogenesis and metastasis. Our results revealed that HO-1 stimulates angiogenesis of pancreatic carcinoma in severe combined immune deficient mice. Overexpression of human hHO-1 after its retroviral transfer into Panc-1 cells did not interfere with tumor growth in vitro. While in vivo the development of tumors was accelerated upon transfection with hHO-1. On the other hand, inhibition of heme oxygenase (HO) activity by stannous mesoporphyrin was able transiently to delay tumor growth in a dose dependent manner. Tumor angiogenesis was markedly increased in Panc-1/hHO-1 compared to mock transfected and wild type. Lectin staining and Ki-67 proliferation index confirmed these results. In addition hHO-1 stimulated in vitro tumor angiogenesis and increased endothelial cell survival. In a lung colonization model, overexpression of hHO-1 increased the occurrence of metastasis, while inhibition of HO activity by stannous mesoporphyrin completely inhibited the occurrence of metastasis. In conclusion, overexpression of HO-1 genes potentiates pancreatic cancer aggressiveness, by increasing tumor growth, angiogenesis and metastasis and that the inhibition of the HO system may be of useful benefit for the future treatment of the disease.

Animals↗
PubMed1981

Differential responses to inducers of delta-aminolaevulinate synthase and haem oxygenase during pregnancy.

The responses of hepatic delta-aminolaevulinate synthase and microsomal haem oxygenase to inducers were examined in pregnant rats. 2-Allyl-2-isopropylacetamide-mediated induction of delta-aminolaevulinate synthase was greatly decreased during pregnancy and in the early post-partum period. Administration of allylisopropylacetamide to pseudopregnant rats induced delta-aminolaevulinate synthase normally. Treatment of pregnant rats with cortisol failed to restore the drug-mediated induction of delta-aminolaevulinate synthase. Microsomal cytochrome P-450 content and the activities of drug-metabolizing enzymes such as aniline hydroxylase and ethylmorphine. N-demethylase were significantly lowered during pregnancy. In contrast with the greatly impaired induction of delta-aminolaevulinate synthase, the induction of haem oxygenase in response to CoCl2 remained unaltered in pregnant rats. The normal perturbations of delta-aminolaevulinate synthase, consisting of an initial inhibition followed by a rebound increase in the enzyme activity associated with CoCL2 treatment, were observed during pregnancy. These findings indicate that hormones and metabolic factors associated with gestation exert significant but differential controls on the induction patterns of delta-aminolaevulinate synthase and haem oxygenase.

5-Aminolevulinate Synthetase↗
PubMed2002

The reactivity of alpha-hydroxyhaem and verdohaem bound to haem oxygenase-1 to dioxygen and sodium dithionite.

Recently we have shown that ferric alpha-hydroxyhaem bound to haem oxygenase-1 can be converted to ferrous verdohaem by approximately an equimolar amount of O2 in the absence of exogenous electrons [Sakamoto, H., Omata, Y., Palmer, G., and Noguchi, M. (1999) J. Biol. Chem.274, 18196-18200]. Contrary to those results, other studies have claimed that the conversion requires both O2 and an electron. More recently, Migita et al. have reported that the major reaction product of ferric alpha-hydroxyhaem with O2 is a ferric porphyrin cation radical that can be converted to ferrous alpha-hydroxyhaem with sodium dithionite [Migita, C. T., Fujii, H., Matera, K. M., Takahashi, S., Zhou, H., and Yoshida, T. (1999) Biochim. Biophys. Acta1432, 203-213]. To clarify the reason(s) for the discrepancy, we compared the reactions; i.e. alpha-hydroxyhaem to verdohaem and verdohaem to biliverdin, under various conditions as well as according to the procedures of Migita. We find that complex formation of alpha-hydroxyhaem with haem oxygenase may be small and a substantial amount of free alpha-hydroxyhaem may remain, depending on the reconstitution conditions; this could lead to a misinterpretation of the experimental results. We also find that ferrous verdohaem appears to be air-sensitive and is therefore easily converted to a further oxidized species with excess O2. Finally, we find that dithionite seems to be inappropriate for investigating the haem oxygenase reaction, because it reduces ferrous verdohaem to a further reduced species that has not been seen in the haem degradation system driven by NADPH-cytochrome P450 reductase.

Carbon Monoxide↗