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 nucleotide sequence of a cDNA for porcine heme oxygenase was determined. The open reading frame encoded a polypeptide of 288 amino acid residues with a molecular mass of 33,074 Da. A prokaryotic expression plasmid carrying porcine heme oxygenase cDNA was constructed and transfected into Escherichia coli cells. The full-length heme oxygenase expressed was localized in the bacterial membranes. Two small-sized heme oxygenases with no membrane-bound properties were also detected, suggesting that in E. coli cells a considerable amount of the enzyme expressed was degraded.
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PMID:Nucleotide sequence of cDNA for porcine heme oxygenase and its expression in Escherichia coli. 128 99

Hepatic heme metabolism and in vitro translation of poly(A) + RNA from livers were studied to elucidate the mechanism of the reduction of microsomal cytochrome P-450 in tumor-bearing mouse livers. Hepatic delta-aminolevulinic acid synthase activity in male C57BL/6N mice (0.203 nmol/mg protein/h) at 8 days after the transplantation of Ehrlich ascites tumor cells was the same level as that of normal livers (0.206 nmol/mg protein/h). On the other hand, hepatic heme oxygenase activity of tumor-bearing mice (0.482 nmol/mg protein/10 min) had increased 8 days following i. p. transplantation of tumor cells when compared with that of normal mouse livers (0.296 nmol/mg protein/10 min). SDS-gel electrophoresis of in vitro translation products of poly(A) + RNA extracted from membrane-bound polysomes of the livers from tumor-bearing mice showed no significant differences from that of normal controls in the region of cytochrome P-450, that is, the molecular weight region of Mr = 47,000-60,000, although microsomal protein content in this region estimated by Coomassie-blue staining was reduced. These results suggest that the decrease of heme biosynthesis or the translation of cytochrome P-450 mRNA played a very small part in the reduction of microsomal cytochrome P-450 in tumor-bearing mice.
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PMID:Heme metabolism and turnover of cytochrome P-450 in tumor-bearing mouse livers. 241 25

The concerted activity of two microsomal enzymes, heme oxygenase and NADPH-cytochrome c (P-450) reductase, is required for isomer-specific oxidation of heme molecule; heme oxygenase is commonly believed to be rate limiting in this activity. In this report, we provide evidence strongly suggesting the rate-limiting role of the reductase in oxidation of heme molecule in rat testis. In the testis and the liver of rats treated with Cd (20 mumol/kg, sc, 24 h) heme oxygenase activity, assessed by the formation of bilirubin, was decreased by 50% and increased by 7-fold, respectively. In these animals, the reductase activity was decreased by nearly 75% in the testis, but remained unchanged in the liver. Similarly, the reductase activity in the liver was not altered when heme oxygenase activity was increased by 20-fold in response to bromobenzene treatment. Addition of purified testicular reductase preparation (purified over 4000-fold), or hepatic reductase, to the testicular microsomes of Cd-treated rats obliterated the Cd-mediated inhibition of heme oxygenase activity. The chromatographic separation of heme oxygenase and the reductase of the testicular microsomal fractions revealed that the reductase activity was markedly decreased (75%) while the heme oxygenase activity, when assessed in the presence of exogenous reductase, was not affected by in vivo Cd treatment. In vitro, the membrane-bound reductase preparation obtained from the testis was more sensitive to the inhibitory effect of Cd than the liver preparation. However, the purified reductase preparations from the testis and the liver exhibited a similar degree of sensitivity to Cd. Based on the molar ratio of heme oxygenase to the reductase in the microsomal membranes of the liver and the testis it appeared that the testicular heme oxygenase, which is predominantly HO-2 isoform, interacts with the reductase less effectively than HO-1; in the induced liver, heme oxygenase is predominantly the HO-1 isoform. It is suggested that due to the low abundance of NADPH-cytochrome c (P-450) reductase and the apparently lower affinity of the enzyme for HO-2, the reductase exerts a regulatory action on heme oxygenase activity in the testis.
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PMID:Cadmium-mediated inhibition of testicular heme oxygenase activity: the role of NADPH-cytochrome c (P-450) reductase. 309 74

A single, intraperitoneal injection of diethyldithiocarbamate (DDTC) to adult, male Sprague-Dawley rats decreased hepatic cytochrome P-450 (P-450) concentrations. This effect was dose-dependent over a range of 250 to 750 mg/kg and most prominent 24-36 hr after dosing. Depletion of hepatic glutathione (GSH) by diethylmaleate (DEM) administration significantly decreased P-450 8 hr after concurrent treatment with DDTC at a dose which given alone had little effect on P-450 concentrations. When hepatic microsomes were incubated with DDTC in the presence of NADPH, P-450 was converted to cytochrome P-420 (P-420). Similar incubations employing [35S]DDTC demonstrated strict NADPH-dependent binding of labeled sulfur to microsomal membranes, suggesting that diminished P-450 concentrations are related to the metabolic activation of DDTC. Addition of reduced GSH to incubation mixtures blocked the binding of 35S to microsomal membranes, as well as conversion of P-450 to P-420. DDTC inhibited NADPH-ADP3+ mediated peroxidation of microsomal lipids in vitro, suggesting that the effect of DDTC on P-450 does not result from stimulation of lipid peroxidation, but may be influenced by the levels of hepatic GSH. DDTC treatment 1 hr after P-450 was pulse labeled by an intravenous injection of [3H]delta-aminolevulinic acid resulted in a 2-fold increase in the rate of loss of radioactivity associated with membrane-bound P-450 heme during the next 20 hr. Within this time interval, hepatic heme oxygenase (HO) activity increased and at 8 hr after dosing was 7-fold greater than control values in the livers, but was unchanged in the kidneys and spleens of DDTC-treated animals. An elevation of hepatic delta-aminolevulinic acid synthetase (delta-ALAS) activity occurred at 8 and 24 hr after DDTC treatment. Since this enzyme is rate limiting in the biosynthesis of heme, its increased activity may represent a compensatory response to offset the DDTC-mediated loss of P-450 heme.
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PMID:Mechanisms of diethyldithiocarbamate-induced loss of cytochrome P-450 from rat liver. 631 Dec 17

The role of membrane-bound IgG present on the membrane of senescent erythrocytes in immune eliminations of aging red cells was investigated. Phagocytosis of populations of red blood cells (RBC) of different ages by autologous monocytes was assessed both by direct phagocytosis and by induction of microsomal heme oxygenase. Removal of IgG from older RBCs inhibited their phagocytosis; in contrast, preincubation of neuraminidase-treated young or in vitro aged RBCs with IgG eluted from old cells led to phagocytosis of RBCs treated by autologous monocytes. It was also found that the Fc portion of membrane-bound IgG is essential for the elimination of senescent cells; less than 15% of old heat-inactivated RBCs coated with F(ab)2 fragment of membrane-bound IgG were phagocytosed. In contrast, more than 50% of old heat-inactivated RBCs coated with heat-eluted IgG were phagocytosed by autologous monocytes. A possible mechanism of elimination of aged cells is discussed.
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PMID:Phagocytosis of senescent erythrocytes by autologous monocytes: requirement of membrane-specific autologous IgG for immune elimination of aging red blood cells. 668 42

Heme oxygenase (HO) catalyzes the first steps in the breakdown of heme to biliverdin and carbon monoxide. It is a membrane-bound protein that has been shown to exist in two isoforms, HO-1 and HO-2. Recently, a soluble, truncated form of rat HO-1 (rHO) lacking the 23 amino-acid membrane anchor has been expressed in E. coli. Extended X-ray absorption fine structure (EXAFS) data on ferric rHO and its fluoride derivative support assignment of the axial iron ligands as oxygen and/or nitrogen donors having distances similar to ferric myoglobin. The electronic absorption and magnetic circular dichroism (MCD) spectra of the ferric and ferrous protoheme complexes of rHO as well as various ligand adducts are very similar to the corresponding spectra of myoglobin. The present study is the first investigation of the heme-heme oxygenase complex with EXAFS and MCD spectroscopy and establishes that the proximal ligand to the heme in rHO is histidine. Furthermore, the close similarity between the electronic absorption and MCD spectra of ferric rHO and myoglobin over the pH range 6 to 10 is consistent with distal heme ligation of ferric rHO as a water molecule or hydroxide ion, depending on pH. Taken together and in conjunction with the results of earlier studies, EXAFS, electronic absorption, and MCD spectroscopy solidly establish that the ligands to the heme in rHO are identical to those in myoglobin, namely, histidine/H2O at low pH and histidine/OH at high pH.
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PMID:Ligation of the iron in the heme-heme oxygenase complex: X-ray absorption, electronic absorption and magnetic circular dichroism studies. 869 42

Heme oxygenase catalyzes the oxidation of heme to biliverdin and carbon monoxide. The gene encoding the truncated soluble rat heme oxygenase-1 (Metl-Pro267) was cloned. The enzyme protein was expressed in E. coli JM109 and purified to homogeneity. The molecular weight of the recombinant enzyme was 30 kDa as assessed by SDS-polyacrylamide gel electrophoresis. From a 3-L culture, about 90 mg of the purified enzyme was routinely obtained. The dependency of the heme oxygenase reaction catalyzed by the soluble enzyme on the NADPH-cytochrome P-450 reductase concentrations and the effect of catalase on the reaction were examined to compare with the purified membrane-bound form of heme oxygenase-1 (Yoshida and Kikuchi, 1978b). The activity of the soluble enzyme was inhibited at high concentrations of NADPH-cytochrome P-450 reductase and the inhibition was not alleviated by addition of catalase unlike the membrane-bound form. The ferric iron of the heme-heme oxygenase complex was in a typical high spin state at acidic to neutral pH (pH 6.5-7.0) but conversion to low spin state was observed at basic pH (pH 9-10). The heme bound to heme oxygenase was converted to biliverdin at a stoichiometric ratio of unity in the presence of NADPH-cytochrome P-450 reductase system. During the heme degradation of the heme-heme oxygenase complex under atmospheric oxygen, several intermediates, that is, oxygenated heme and verdoheme, were spectrally discriminated.
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PMID:Cloning and expression of cDNA for soluble form of rat heme oxygenase-1. 902 1

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

Endogenous carbon monoxide (CO) contributes to vasodilator responses of cerebral microvessels in newborn pigs. We investigated the expression, intracellular localization, and activity of heme oxygenase (HO), the key enzyme in CO production, in quiescent cerebral microvascular endothelial cells (CMVEC) from newborn pigs. HO-1 and HO-2 isoforms were detected by RT-PCR, immunoblotting, and immunofluorescence. HO-1 and HO-2 are membrane-bound proteins that have a strong preference for the nuclear envelope and perinuclear area of the cytoplasm. Betamethasone (10(-6) to 10(-4) M for 48 h) was associated with upregulation of HO-2 protein by approximately 50% and inhibition of Cox-2 but did not alter HO-1 or endothelial nitric oxide synthase expression in CMVEC. In vivo betamethasone treatment of newborn pigs (0.2 and 5.0 mg/kg im for 48 h) upregulated HO-2 in cerebral microvessels by 30-60%. HO activity as (14)CO production from [(14)C]glycine-labeled endogenous heme was inhibited by chromium mesoporphyrin (10(-6) to 10(-4) M). L-Glutamate (0.3-1.0 mM) stimulated HO activity 1.5-fold. High-affinity specific binding sites for L-[(3)H]glutamate suggestive of the glutamate receptors were detected in CMVEC. Altogether, these data suggest that, in cerebral circulation of newborn pigs, endothelium-derived CO may contribute to basal vascular tone and to responses that involve glutamate receptor activation.
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PMID:Cerebral vascular endothelial heme oxygenase: expression, localization, and activation by glutamate. 1169 54

Most of the iron required for erythropoiesis is provided by heme iron recycling following degradation of senescent erythrocytes by tissue macrophages. Accumulation of biochemical modifications at the red blood cell membrane during ageing (externalisation of phosphatidyl-serine, peroxydation of membrane-bound lipoproteins, loss of sialic acid residues and formation of senescence neoantigens) constitute a series of signals that will allow the macrophage to identify the red blood cells to be eliminated, through interaction with specific receptors. After this initial recognition step, the red blood cell is internalised by phagocytosis, and phagosome maturation, which can comprise recruitment of the endoplasmic reticulum, will favour degradation of red blood cell constituents. Heme is catabolised by heme oxygenase 1, anchored in the endoplasmic reticulum membrane. A fraction of the released iron will be recycled back to the plasma through ferroportin, a membrane-bound Fe (II) export molecule, and a fraction will retained within the ferritin molecules, to be released at later stages. Multiple evidence coming from human diseases (type 4 hemochromatosis) and animal models indicate that ferroportin is essential for heme iron recycling by macrophages. Furthermore, ferroportin seems to be the molecular target of hepcidin, this circulating peptide synthesized by the liver and acting as a negative regulator of intestinal iron absorption and iron recycling by macrophages. Perturbations in erythrophagocytosis play a physiopathological role in several diseases, including hemochromatosis, anemia of chronic disorders and thalassemia.
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PMID:[Erythrophagocytosis and recycling of heme iron in normal and pathological conditions; regulation by hepcidin]. 1592 1


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