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:1.14.99.3 (heme oxygenase)
4,196 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The administration of aflatoxin B1 (AFB1) in New Zealand rabbit for 5 days at a daily oral dose of 0.05 or 0.1 mg/kg decreased microsomal hepatic cytochrome P450 whereas a dose-dependent increase in the reduced microsomal 420 nm absorption occurred. The nature of such an absorption was then investigated. Either in vitro incubation of control microsomal proteins with AFB1 up to 800 microM and NADPH, or primary rabbit hepatocyte cultures exposure to AFB1 up to 30 microM for 24 to 72 h, failed to produce any 420 nm absorbing species, suggesting that the 420 nm absorption observed in vivo was due to an hemoprotein increase. Chemical reductions of microsomal proteins from AFB1-treated rabbits confirmed this hypothesis. Enzyme activity determinations revealed an increase in both microsomal heme oxygenase and NADPH-cytochrome c reductase activities in AFB1 treated rabbits, suggesting that the 420 nm absorption observed in vivo was related to a particular increase in heme oxygenase.
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PMID:Reduced cytochrome P450 and increased heme oxygenase in liver during rabbit aflatoxicosis. 863 14

In the course of our studies on the local blood flow modulation in the NMRI-mouse placenta we have focussed on regulatory pathways involving recently appreciated gaseous messenger molecules nitric oxide (NO) and carbon monoxide (CO), which are generated by NO synthase (NOS) and heme oxygenase (HO)-2, respectively. The distribution of NOS was investigated by immunohistochemistry using an antiserum to the neuronal isoform (NOS-I) and by NADPH diaphorase (NADPHd) histochemistry, supplemented with procedures (permanganate and formaldehyde method) serving to enhance the specificity of the enzyme histochemical method for NOS visualization. HO-2 was demonstrated immunohistochemically. In addition, cyclic guanosine monophosphate (cGMP)-forming soluble guanylate cyclase (sGC) and dehydrogenases generating the NOS co-substrate NADPH were analysed either by immunohistochemistry or enzyme histochemistry. NOS-I immunostaining was observed in the intraplacental visceral yolk sac epithelial cells but not in the placenta and extraplacental visceral epithelial yolk sac cells. Co-localization of NOS-I immunolabeling and NOS-associated NADPHd was exclusively found in the intraplacental visceral epithelial cells, while NADPHd activity not associated to NOS was present in other placental and extraplacental cells additionally analysed for control reasons. HO-2 and sGC immunoreactivity could not be detected in the placenta including the intraplacental visceral epithelial cells but were expressed in several extraplacental cells. Dehydrogenases producing the NOS co-substrate NADPH were present in the intraplacental visceral epithelium as well as in other placental and extraplacental cells. Since the intraplacental visceral epithelial yolk sac layer closely accompanies large fetal blood vessels entering the placental labyrinth from the chorionic plate it may be assumed that NO, generated by the NADPH-consuming NOS-I in the intraplacental yolk sac epithelium, acts to regulate the blood flow by relaxing smooth muscle cells in the wall of these fetal vessels. The lack of immunoreactivity to the NO-effector molecule sGC may be due to methodological reasons. The absence of the HO-2/CO system suggests its insignificant role as a potential gas signaling pathway in the vascular smooth muscle system of the intraplacental visceral yolk sac of mice.
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PMID:Nitric oxide synthase I immunoreactivity and NOS-associated NADPHd histochemistry in the visceral epithelial cells of the intraplacental mouse yolk sac. 873 2

Microsomal heme oxygenase (HO) is a cytochrome P-450-assisted oxidoreductase, which catalyzes the NADPH-dependent decomposition of heme to carbon monoxide (CO), biliverdin, and iron. Recent evidence suggests that CO, similar to nitric oxide (NO), may serve as gaseous biological signalling molecule, which acts by stimulating soluble guanylate cyclase in target cells. In the present investigation, we report the HO-like immunoreactivity (LIR) pattern of the constitutive HO isozyme, HO-2, and compare the results with recently published data on constitutive NO-producing nitric oxide synthase (NOS) in rat tissues. HO-2-LIR was most consistently observed in connective tissue elements (fibrocytes/-blasts and fibroblast-like cells, such as interstitial cells in the bowel), blood vessel wall constituents (arterial and venous endothelial cells, vascular smooth muscle cells), visceral smooth muscle cells (airway musculature, myometrium, muscularis mucosae of the small intestine), mesothelial cells of serous membranes and in select epithelial cell populations. HO-2-LIR was absent from the striated (skeletal and cardiac) musculature. HO-2 had a more widespread distribution and its expression largely differs from that of NOS. HO-2-LIR and NOS appear to be co-expressed in vascular endothelial cells and in selected nerve cell populations of certain parasympathetic and probably sensory ganglia. Our data suggest potential CO and NO systems as interrelated regulatory pathways in the local paracrine and autocrine control of diverse functional systems.
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PMID:Expression of heme oxygenase-2 (HO-2)-like immunoreactivity in rat tissues. 873 5

Biliverdin reductase is classified into two isoforms in substrate specificity; biliverdin-IX alpha reductase and biliverdin-IX beta reductase with a molecular mass of 22 kDa and 34-42 kDa, respectively. We have cloned the cDNA encoding human biliverdin-IX alpha reductase from MOLT4 cDNA library. The cDNA of 1146 bp in nucleotide length contained an entire reading frame coding 296 amino acid residues. The NADH/NADPH binding consensus sequence was found in the amino-terminal region. Comparison between human and rat biliverdin-IX alpha reductases showed 82.8% identity in amino acid sequences and 80.3% identity in the coding nucleotides. The amino acid sequence of human biliverdin-IX alpha reductase showed no significant homology to that of human biliverdin-IX beta reductase. Northern blot analysis of poly(A) RNA from eight different human tissues revealed that the reductase mRNA was abundant in the brain, lung and pancreas but not in the liver. The distribution pattern of biliverdin-IX alpha message was different from that of heme oxygenase activity which is known to be high in the liver and to be low in the heart and lung.
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PMID:Cloning and characterization of the cDNA encoding human biliverdin-IX alpha reductase. 895 Jan 84

Heme oxygenase activity is the sole known physiological source for the production of carbon monoxide (CO), a gaseous messenger candidate. A sensitive radioenzymatic microassay was validated to study regional distribution of heme oxygenase activity within the rat brain. The assay utilized a 14,000 X g supernatant of brain homogenate and [14C]heme as the substrate. Thin layer chromatography revealed that incubation of cerebellar supernatant with (14C]heme yielded a single reaction product, indistinguishable from bilirubin, that was selectively extracted into toluene. Radioactivity in toluene increased linearly in respect to time and added protein, was totally dependent on NADPH and was not detected with boiled homogenate. The reaction was dose-dependently inhibited by Zn-protoporphyrin IX (IC50 0.3 microM) and by an antibody generated against rat NADPH-cytochrome P450 reductase indicating specific involvement of heme oxygenase. As little as 36 fmol [14C]bilirubin/min could be readily detected requiring only microgram-quantities of cerebellar homogenate. Heme oxygenase activity measurements from discrete brain regions revealed for the first time marked differences in enzyme activity with the increasing order: frontal cortex < cerebellum = caudate-putamen < hippocampus = hypothalamus = colliculi << trapezoid body. This activity pattern closely reflects the distribution of immunoreactivity and mRNA for heme oxygenase. The present microassay should offer a valuable tool for studies directly assessing a possible role for CO in neural signaling.
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PMID:A sensitive microassay reveals marked regional differences in the capacity of rat brain to generate carbon monoxide. 897 51

Heme is a tetrapyrrolic ring with iron as the central metal atom and acts as a prosthetic group for a number of enzymes, e.g. cytochromes and globins. It also plays an important role in the regulation of transcription, translation, protein translocation and erythroid differentiation. Thus, heme regulation is under strict control in the body. Our studies on the regulatory enzymes of heme anabolism, aminolevulinic acid synthetase (ALA-S), and of catabolism, heme oxygenase (HMOX), in the spleen has revealed that cobalt protoporphyrin acts as an inducer of HMOX. It is revealed that by alteration of side groups at C2 and C4 changes the nature of action of Co-protoporphyrin from an inducer to a strong inhibitor of HMOX activity. All the three analogues Co-protoporphyrin, Co-mesoporphyrin and Co-hematoporphyrin have been shown to induce the ALA-S activity to the similar extent. NADPH-cytochrome c reductase, a microsomal membrane bound enzyme, is required by HMOX for the enzymatic conversion of heme into biliverdin IXc and is also required for NADPH-dependent lipid peroxidation in the microsomes. It has been observed that Co-mesoporphyrin causes an inhibition of HMOX activity and consequently leads to an induced level of microsomal NADPH-dependent lipid peroxidation.
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PMID:In heme catabolism C2 and C4 vinyl groups reduction of cobalt protoporphyrin forms cobalt mesoporphyrin and alters the nature of action of the metalloporphyrin in vivo. 898 Sep 27

Microsomal NADPH-cytochrome P450 reductase (CPR) is one of only two mammalian enzymes known to contain both FAD and FMN, the other being nitric-oxide synthase. CPR is a membrane-bound protein and catalyzes electron transfer from NADPH to all known microsomal cytochromes P450. The structure of rat liver CPR, expressed in Escherichia coli and solubilized by limited trypsinolysis, has been determined by x-ray crystallography at 2.6 A resolution. The molecule is composed of four structural domains: (from the N- to C- termini) the FMN-binding domain, the connecting domain, and the FAD- and NADPH-binding domains. The FMN-binding domain is similar to the structure of flavodoxin, whereas the two C-terminal dinucleotide-binding domains are similar to those of ferredoxin-NADP+ reductase (FNR). The connecting domain, situated between the FMN-binding and FNR-like domains, is responsible for the relative orientation of the other domains, ensuring the proper alignment of the two flavins necessary for efficient electron transfer. The two flavin isoalloxazine rings are juxtaposed, with the closest distance between them being about 4 A. The bowl-shaped surface near the FMN-binding site is likely the docking site of cytochrome c and the physiological redox partners, including cytochromes P450 and b5 and heme oxygenase.
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PMID:Three-dimensional structure of NADPH-cytochrome P450 reductase: prototype for FMN- and FAD-containing enzymes. 923 90

Aflatoxin B1 (AFB1) has been reported to decrease microsomal hepatic cytochrome P450 (P450) content and increase both total plasma bilirubin concentration and liver heme oxygenase activity. The purposes of this study were to determine whether liver hemoproteins contents and heme catabolizing enzymes were affected by the mycotoxin and whether these alterations were linked to hyperbilirubinemia. Male New Zealand rabbits were divided into three groups of five animals, each receiving for 5 days either arabic gum as vehicle or AFB1 at a daily oral dose of 0.05 or 0.10 mg/kg. These treatments affected neither cytochrome b5 content nor NADPH-cytochrome reductase activity. A linear dose-dependent decrease in cytochrome P450 content and increases in both heme oxygenase and biliverdin reductase activities were observed. Bilirubin UDP-glucuronyltransferase activity was dramatically decreased at both doses, whereas cholestasis occurred only at 0.10 mg/kg. An exponential dose-dependent increase in plasma bilirubin concentration was also observed. Both the simultaneous exponential increase in bilirubinemia associated to a reduced bilirubin UDP-glucuronyltransferase activity and the absence of cholestasis at 0.05 mg/kg, suggested that the hyperbilirubinemia is more probably related to an increased heme catabolism than to an altered bile duct permeability.
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PMID:Dose-related increase in liver heme catabolism during rabbit aflatoxicosis. 929 32

A full-length heme oxygenase gene from the pathogenic bacterium Corynebacterium diphtheriae has been subcloned and expressed in Escherichia coli. The enzyme is expressed at high levels as a soluble catalytically active protein that results in the accumulation of biliverdin within the E. coli cells. The purified heme oxygenase forms a 1:1 complex with heme (Kd = 2.5 +/- 1 microM) and has hemeprotein spectra similar to those previously reported for the purified eukaryotic heme oxygenases. In the presence of an E. coli NADPH-dependent reductase isolated during the purification of Hmu O, the heme-Hmu O complex is catalytically turned over to yield biliverdin IXalpha and carbon monoxide. A number of redox partners were investigated for their ability to reconstitute Hmu O activity in vitro. Of these the most efficient appeared to be the recombinant NADH-dependent putidaredoxin/putidaredoxin reductase from Pseudomonas putida. As with the E. coli NADPH-dependent reductase the final products of the reaction were biliverdin IXalpha and carbon monoxide. This is the first bacterial heme oxygenase to be described to date. The close relationship between iron acquisition and pathogenesis suggests that the release of iron from heme by heme oxygenase may play a crucial role in the pathogenicity of C. diphtheriae.
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PMID:Expression and characterization of a heme oxygenase (Hmu O) from Corynebacterium diphtheriae. Iron acquisition requires oxidative cleavage of the heme macrocycle. 942 39

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.
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PMID:Crystal structure of rat heme oxygenase-1 in complex with heme. 1076 May 13


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