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 present investigation provides evidence of the ability of Sn-protoporphyrin to cause striking alterations in adrenal and testicular cytochrome P-450-dependent steroidogenesis and defines the potential of this metalloporphyrin to serve as a cellular toxin. Sn-protoporphyrin is currently used on an experimental basis for treatment of hyperbilirubinemias in humans, including newborn infants. Specifically, in the adrenals of rats treated with a moderate regimen of Sn-protoporphyrin (two doses of 50 mumol/kg, s.c.), marked decreases of 60 to 70% in the microsomal 21 alpha-hydroxylase and the mitochondrial 11 beta-hydroxylase activities were observed after 7 days. Concomitant with these decreases was a significant depression in the adrenal mitochondrial cytochrome P-450 content and a notable reduction (approximately 30%) in serum corticosterone levels. Similarly, in the testes, significant decreases in the microsomal and mitochondrial cytochrome P-450 contents and the microsomal 17 alpha-hydroxylase activity were observed. Serum testosterone level, however, was not decreased, reflecting an absence of decrease in side chain cleavage activity. Metalloporphyrin caused a striking decrease of 65 to 80% in the microsomal heme oxygenase activity in the testes and the adrenals, as well as significant reductions in NADPH-cytochrome P-450 reductase activity of the organs. The decrease in heme oxygenase activity, however, as suggested by Western immunoblotting, apparently resulted, to a large extent, from the loss of enzyme protein integrity rather than a competitive inhibition of activity. At the transcript level, Northern blot analysis using a full length rat testis cDNA probe for heme oxygenase-2 mRNA indicated that Sn-protoporphyrin treatment did not decrease the amount of message for either of the heme oxygenase-2 transcripts (1.3 and 1.9 Kb).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Tin-protoporphyrin: a potent inhibitor of hemoprotein-dependent steroidogenesis in rat adrenals and testes. 137 Nov 61

We show by Northern blot analysis that human HO-2 is encoded by two transcripts (1.3 and 1.7 kb) and is a single-copy gene as judged by Southern blot analysis. We further provide evidence based on Northern blot and sequence analysis of a cDNA representing the larger transcript that the transcripts differ in the 3' untranslated region. A 274-base-pair DNA fragment from the rat heme oxygenase-2 gene (I. Cruse and M.D. Maines, 1988, J. Biol. Chem. 263, 3348-3353) was used to isolate a human HO-2 cDNA from a fetal kidney library in lambda gt11. The clone, designated hK-1, was sequenced and the cDNA insert was determined to be 1625 base pairs in length, encoding a protein of 313 amino acids. Two consensus polyadenylation signals separated by 440 nucleotides were identified in the 3' untranslated region. The size of the cDNA insert closely approximated the larger of two mRNAs. The nucleotide sequence was 88% identical to the rat HO-2 gene within the predicted coding region and the putative translation product was also estimated to be 88% identical to the rat gene product (M. O. Rotenberg and D. Maines, 1990, J. Biol. Chem. 265, 7501). The predicted size, 36 kDa, corresponded well with HO-2 detected in human testis microsomes by Western blot analysis. Further, the fusion protein expressed in Escherichia coli displayed significant heme oxygenase activity, which was inhibited by Zn- and Sn-protoporphyrins, known inhibitors of eukaryotic heme oxygenase, but not by sulfhydryl reagents.
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PMID:Human heme oxygenase-2: characterization and expression of a full-length cDNA and evidence suggesting that the two HO-2 transcripts may differ by choice of polyadenylation signal. 157 8

Chinese hamster ovary cells cultured in vitro were used to assess the role of glutathione metabolism in the induction of the 32-kDa stress protein. Enhanced synthesis of the 32-kDa protein was observed after cells were incubated with CdCl2 or diethylmaleate and protein was subjected to SDS-PAGE followed by fluorography. Concomitantly, in both cell preparations an increase in heme oxygenase activity was observed. Proteins from CdCl2- and diethylmaleate-treated cells were subjected to Western blotting and protein crossreacting with either rabbit antibody to rat liver heme oxygenase-1 (32,000 Mr) or rat testis heme oxygenase-2 (36,000 Mr) quantitated. The analysis indicated that the CdCl2 treatment increased the intensity of the HO-1 band 5.5-fold while the diethylmaleate treatment increased it three-fold relative to control. Neither treatment affected the intensity of HO-2 antibody binding. Incubation of cells with buthionine sulfoximine, under conditions which resulted in greater than or equal to 90% of the intracellular glutathione being depleted, enhanced synthesis of a 32-kDa protein when assayed by SDS-PAGE. This protein exhibited a Mr similar to the 32-kDa protein induced by either CdCl2 or diethylmaleate treatment. Proteins from buthionine sulfoximine and diethylmaleate-treated cells were mixed together and subjected to 2D PAGE. The resulting fluorograph demonstrated that both treatments produced identical patterns. In contrast, incubation of cells in diamide, a thiol oxidizing compound, resulted in enhanced synthesis of the 110-, 90-, and 73-kDa heat shock proteins but not the 32-kDa protein. The data presented have shown that depletion of glutathione by two independent methods, conjugation and inhibition of synthesis, enhances the synthesis of a 32-kDa protein identified as heme oxygenase-1; oxidation of glutathione, on the other hand did not. We interpret this to indicate that glutathione depletion rather than conjugation or oxidation represents one pathway for induction of heme oxygenase-1.
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PMID:Enhancement of heme oxygenase-1 synthesis by glutathione depletion in Chinese hamster ovary cells. 189 36

A 1.3-kb rat testis cDNA clone for heme oxygenase-2 (HO-2) was used as a Northern blot hybridization probe, and a single homologous mRNA species, of approximately 1.3 kb in rabbit brain and testis was detected. This contrasted with the observation made with rat brain in which two HO-2 transcripts of approximately 1.3 and 1.9 kb were detected. Use of the same rat HO-2 probe to screen a rabbit brain cDNA library in lambda gt11 resulted in the recovery of a single 1.2-kb cDNA clone. This cDNA exhibits 84% overall nucleotide sequence homology with rat HO-2 and encodes a protein of 35,352 Da, displaying 88% amino acid sequence homology with rat testis HO-2. Furthermore, when expressed in Escherichia coli, the rabbit cDNA-encoded protein displays heme oxygenase activity and cross-reactivity with antibody to rat HO-2. Based on findings obtained through Western immunoblot analysis of partially purified HO-2 protein prepared from rabbit testis and brain, the 35- to 36-kDa molecular form appears to be the major HO-2 form detected in the brain, whereas a 42-kDa species is the predominant form observed in rabbit testis. Having deduced the amino acid sequence of rabbit brain HO-2, we provide a comparison of this sequence with those of rat, mouse, and human HO-1 and rat HO-2, and thereby identify a 24-amino-acid-long peptide region which, except for one residue, is identical in all five species of HO-1 and HO-2 compared (96% similarity), and exhibits 100% similarity in predicted secondary structure (for this region) in all five proteins. We propose that this peptide may be important to the heme binding and isomer-specific tetrapyrrole cleavage activities of the heme oxygenase isozymes.
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PMID:Characterization of a cDNA-encoding rabbit brain heme oxygenase-2 and identification of a conserved domain among mammalian heme oxygenase isozymes: possible heme-binding site? 192 2

A major inducible form of heme oxygenase (EC 1.14.99.3) was purified from liver microsomes of chicks pretreated with cadmium chloride. The purification involved solubilization of microsomes with Emulgen 913 and sodium cholate, followed by DEAE-Sephacel, carboxymethyl-cellulose (CM-52) and hydroxyapatite chromatography, and FPLC through Superose 6 and 12 columns operating in series. The final product gave a single band on silver-stained SDS/polyacrylamide gels (Mr = 33,000). Optimal conditions for measurement of activity of solubilized heme oxygenase were studied. In a reconstituted system containing purified heme oxygenase, NADPH-cytochrome reductase, biliverdin reductase and NADPH, the Km for free heme was 3.8 +/- 0.5 microM; for heme in the presence of bovine serum albumin (5 mol heme/3 mol albumin) the Km was 5.0 +/- 0.8 microM; and the Km for NADPH was 6.1 +/- 0.4 microM (all values mean +/- SD, n = 3). Oxygen concentration as low as 15 microM, with saturating concentrations of heme and NADPH, did not affect the reaction rate, indicating that the supply of oxygen is not involved in the physiological regulation of activity of the enzyme. The pH optimum of the reaction was 7.4; at 37 degrees C, the apparent Vmax was 580 +/- 44 nmol biliverdin.(mg protein)-1.min-1 and the molecular activity was 19.2 min-1. Biliverdin IXa was the sole biliverdin isomer formed. In the presence of purified biliverdin reductase, biliverdin was converted quantitatively to bilirubin. Addition of catalase to the reconstituted system decreased the breakdown of heme to non-biliverdin products and led to nearly stoichiometric conversion of heme to biliverdin. Activity of the enzyme in the reconstituted system was inhibited by metalloporphyrins in the following order of decreasing potency: tin mesoporphyrin greater than tin protoporphyrin greater than zinc protoporphyrin greater than manganese protoporphyrin greater than cobalt protoporphyrin. Protoporphyrin (3.3 or 6.6 microM) (and several other porphyrins) and metallic ions (100 microM) alone had little if any inhibitory effect, except for Hg2+ which inhibited by 67% at 10 microM and totally at 15 microM. Following partial cleavage, fragments of the purified enzyme were sequenced. Comparison of sequences to those derived from cDNA sequences for the major inducible rat and human heme oxygenase showed 69% and 76% similarities, respectively. The histidine residue at position 132 of rat heme oxygenase-1 and the residues (Lys128-Arg136) flanking His132 were conserved in all three enzymes, as well as in the corresponding portion of a fourth less highly similar rat enzyme, heme oxygenase-2.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Purification and characterization of heme oxygenase from chick liver. Comparison of the avian and mammalian enzymes. 215 89

In a recent study (Cruse, I., and Maines, M.D. (1988) J. Biol. Chem. 263, 3348-3353), we reported the isolation of a small cDNA fragment encoding a portion of heme oxygenase-2 through immunological screening of a rat testis cDNA library in lambda gt11. We have now used this 274-base pair (bp) cDNA fragment as a hybridization probe for rescreening of the same library, and have thereby recovered a number of additional positive isolates. Of these, three candidates of approximately 900, 1100, and 1300 bp, respectively, were subsequently subcloned and sequenced. Although differing in length, the sequences of these clones were found to be otherwise identical. Moreover, the length of isolate 18B, 1284 bp, corresponded well with that of the single mRNA species (approximately 1300-1350 nucleotides) detected through Northern blot hybridization analysis of rat testis total and poly(A)+RNA. This full- or near full-length cDNA encodes a 315-amino acid protein with a molecular weight of 35,757, in good agreement with the 36,000 estimated molecular weight of heme oxygenase-2. When expressed in Escherichia coli, cDNA encodes a protein that cross-reacts with heme oxygenase-2 antiserum (as assayed by Western immunoblotting) and yields high levels of heme oxygenase activity in bacterial soluble cell extracts. Finally, computer analysis of the heme oxygenase-2 cDNA sequence indicates that the predicted amino acid sequence and hydropathy profile of the heme oxygenase-2 protein exhibit similarity with heme oxygenase-1.
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PMID:Isolation, characterization, and expression in Escherichia coli of a cDNA encoding rat heme oxygenase-2. 218 51

Two isoforms of the enzyme heme oxygenase are expressed in distinct populations of neurons in the brain. These enzymes catalyse the oxidative cleavage of heme to the cellular antioxidant biliverdin resulting in the release of carbon monoxide in the process. Both heme and carbon monoxide may play important roles in regulating the nitric oxide-cyclic guanosine monophosphate signal transduction system. Thus we have examined the distributions of both isoforms of heme oxygenase in the rat brain, and compared their localizations with that of nitric oxide synthase determined with the NADPH-diaphorase histochemical technique. Heme oxygenase-1 is highly expressed in a few select populations of neurons including cells in the hilus of the dentate gyrus, in the hypothalamus, cerebellum and brainstem. This enzyme appears to be coexpressed with nitric oxide synthase only in a few cells in the dentate gyrus. Heme oxygenase-2 is much more widely expressed. It is present in mitral cells in the olfactory bulb, pyramidal cells in the cortex and hippocampus, granule cells in the dentate gyrus, many neurons in the thalamus, hypothalamus, cerebellum and caudal brainstem. However, only some of these labelled neurons also displayed nitric oxide synthase. Instead, many neurons expressing heme oxygenase-2 correspond to those known to express high levels of the hemoprotein soluble guanylyl cyclase. These results suggest that heme oxygenase may play a role in modulating guanylyl cyclase independent of nitric oxide synthase. This may result from regulation of intracellular heme and carbon monoxide levels by the heme oxygenase system.
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PMID:Brain heme oxygenase isoenzymes and nitric oxide synthase are co-localized in select neurons. 753 81

Heme oxygenase exists as two isoenzymes designated heme oxygenase-1 (HO-1) and heme oxygenase-2 (HO-2). HO-2 is made constitutively in many cell types whereas HO-1 is a stress protein inducible by heat, heavy metals, ultraviolet irradiation, and oxidative stress. Recombinant rat HO-1 was expressed in bacteria and antiserum designated HO-1713 was raised against the purified protein. HO-1713 detected recombinant rat HO-1 and recombinant rat HO-2. In rat tissues it detected HO-1 and a second, unidentified band designated HO-L (heme oxygenase-like immunoreactivity) which was not HO-2. Cultured rat cortical neurons and forebrain astrocytes were exposed to hydrogen peroxide (0.14-0.7 micromolar for 30 or 60 min). Neurons which contained little detectable HO-1 and which were sensitive to hydrogen peroxide at the high end of the dose curve failed to induce HO-1 by Western blot analysis. In contrast, cultured rat forebrain astrocytes which contained HO-1 under normal culture conditions and which were resistant to injury by hydrogen peroxide, increased their content of immunoreactive HO-1 by 7-fold within 3 h after exposure. Our results support a protective role for HO-1 in oxidative injury and suggest that the relative inability of neurons to increase HO-1 after oxidative stress may contribute to their selective vulnerability vis-a-vis astrocytes. They also suggest that differential expression of heme oxygenase in studies utilizing CNS cultures may alter normal cell physiology and cell survival.
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PMID:Differential expression of heme oxygenase-1 in cultured cortical neurons and astrocytes determined by the aid of a new heme oxygenase antibody. Response to oxidative stress. 760 42

Carbon monoxide (CO), produced endogenously by heme oxygenase, has been implicated as a neuronal messenger. Carotid bodies are sensory organs that regulate ventilation by responding to alterations of blood oxygen, CO2, and pH. Changes in blood gases are sensed by glomus cells in the carotid body that synapse on afferent terminals of the carotid sinus nerve that projects to respiratory-related neurons in the brainstem. Using immunocytochemistry, we demonstrate that heme oxygenase 2 is localized to glomus cells in the cat and rat carotid bodies. Physiological studies show that zinc protoporphyrin IX, a potent heme oxygenase inhibitor, markedly increases carotid body sensory activity, while copper protoporphyrin IX, which does not inhibit the enzyme, is inactive. Exogenous CO reverses the stimulatory effects of zinc protoporphyrin IX. These results suggest that glomus cells are capable of synthesizing CO and endogenous CO appears to be a physiologic regulator of carotid body sensory activity.
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PMID:Carbon monoxide: a role in carotid body chemoreception. 789 14

Heme oxygenase is an essential enzyme in heme catabolism that cleaves heme to form biliverdin, releasing carbon monoxide and iron. There are two isozymes of heme oxygenase: heme oxygenase 1 (HO-1) and heme oxygenase 2, each of which is encoded by a separate gene. It is noteworthy that HO-1 is inducible by various environmental factors, while heme oxygenase 2 is not. Here we have localized the human HO-1 gene to chromosome 22 by polymerase chain reaction (PCR) analysis of human-hamster somatic cell hybrids. The precise region of the HO-1 locus was then determined by fluorescence in situ hybridization, revealing that the human HO-1 gene is localized to 22q12.
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PMID:Mapping of the human gene for inducible heme oxygenase to chromosome 22q12. 794 May 28


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