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Günter F. Wildner - One of the best experts on this subject based on the ideXlab platform.
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Formation of the tight-binding inhibitor, 3-ketoarabinitol-1,5-bisphosphate by ribulose-1,5-bisphosphate carboxylase/Oxygenase is O_2-dependent
Photosynthesis Research, 1998Co-Authors: Genhai Zhu, Richard G Jensen, Hans J. Bohnert, Günter F. WildnerAbstract:Ribulose-1,5-bisphosphate carboxylase/Oxygenase (Rubisco) (EC 4.1.1.39) not only catalyzes carboxylation and oxygenation of ribulose-1,5-bisphosphate (RuBP), but it can also act either as an epimerase or isomerase converting RuBP into xylulose-1,5-bisphosphate (XuBP) or 3-ketoarabinitol-1,5-bisphosphate (KABP), respectively, a process called misfire. XuBP is formed as a result of misprotonation at C3 of the RuBP-enediol. It is released from Rubisco active sites and accumulates in the Reaction mixture. Increasing the amounts of CO_2 or O_2 decreases XuBP production. However, KABP synthesis, which has been proposed to be only a product due to C2 misprotonation of the RuBP-endiol, is dependent upon the presence of O_2. KABP remains tightly bound to Rubisco active sites after its formation, causing the loss of Rubisco activity (‘fallover’). The results suggest that the non-stabilized form of the peroxy-intermediate in the Oxygenase Reaction can be converted in a backReaction to KABP and molecular oxygen. The stabilization of the peroxy-intermediate due to the presence of Mn^2+ instead of Mg^2+ eliminates the formation of KABP.
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simple determination of the co2 o2 specificity of ribulose 1 5 bisphosphate carboxylase Oxygenase by the specific radioactivity of 14c glycerate 3 phosphate
Plant Physiology, 1992Co-Authors: Genhai Zhu, Richard G Jensen, Richard B Hallick, Günter F. WildnerAbstract:A new method is presented for measurement of the CO(2)/O(2) specificity factor of ribulose-1,5-bisphosphate carboxylase/Oxygenase (Rubisco). The [(14)C]3-phosphoglycerate (PGA) from the Rubisco carboxylase Reaction and its dilution by the Rubisco Oxygenase Reaction was monitored by directly measuring the specific radioactivity of PGA. (14)CO(2) fixation with Rubisco occurred under two Reaction conditions: carboxylase with Oxygenase with 40 micromolar CO(2) in O(2)-saturated water and carboxylase only with 160 micromolar CO(2) under N(2). Detection of the specific radioactivity used the amount of PGA as obtained from the peak area, which was determined by pulsed amperometry following separation by high-performance anion exchange chromatography and the radioactive counts of the [(14)C]PGA in the same peak. The specificity factor of Rubisco from spinach (Spinacia oleracea L.) (93 +/- 4), from the green alga Chlamydomonas reinhardtii (66 +/- 1), and from the photosynthetic bacterium Rhodospirillum rubrum (13) were comparable with the published values measured by different methods.
Masato Noguchi - One of the best experts on this subject based on the ideXlab platform.
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conformational equilibrium of nadph cytochrome p450 oxidoreductase is essential for heme Oxygenase Reaction
Antioxidants, 2020Co-Authors: Masakazu Sugishima, Masato Noguchi, Junichi Taira, Tatsuya Sagara, Ryota Nakao, Hideaki Sato, Keiichi Fukuyama, Ken Yamamoto, Takuo Yasunaga, H SakamotoAbstract:Heme Oxygenase (HO) catalyzes heme degradation using electrons supplied by NADPH–cytochrome P450 oxidoreductase (CPR). Electrons from NADPH flow first to FAD, then to FMN, and finally to the heme in the redox partner. Previous biophysical analyses suggest the presence of a dynamic equilibrium between the open and the closed forms of CPR. We previously demonstrated that the open-form stabilized CPR (ΔTGEE) is tightly bound to heme–HO-1, whereas the reduction in heme–HO-1 coupled with ΔTGEE is considerably slow because the distance between FAD and FMN in ΔTGEE is inappropriate for electron transfer from FAD to FMN. Here, we characterized the enzymatic activity and the reduction kinetics of HO-1 using the closed-form stabilized CPR (147CC514). Additionally, we analyzed the interaction between 147CC514 and heme–HO-1 by analytical ultracentrifugation. The results indicate that the interaction between 147CC514 and heme–HO-1 is considerably weak, and the enzymatic activity of 147CC514 is markedly weaker than that of CPR. Further, using cryo-electron microscopy, we confirmed that the crystal structure of ΔTGEE in complex with heme–HO-1 is similar to the relatively low-resolution structure of CPR complexed with heme–HO-1 in solution. We conclude that the “open–close” transition of CPR is indispensable for electron transfer from CPR to heme–HO-1.
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Hydroxylamine and hydrazine bind directly to the heme iron of the heme-heme Oxygenase-1 complex.
Journal of inorganic biochemistry, 2004Co-Authors: Hiroshi Sakamoto, Masakazu Sugishima, Keiichi Fukuyama, Yuichiro Higashimoto, Shunsuke Hayashi, Graham Palmer, Masato NoguchiAbstract:We investigated whether or not hydroxylamine (HA) and hydrazine (HZ) interact with heme bound to heme Oxygenase-1. Anaerobic addition of either HA or HZ to the ferric heme-enzyme complex produced a low-spin heme species. Titration studies at different pHs revealed that the neutral form of each of HA and HZ selectively binds to the heme with dissociation constants of 9.8 and 1.8 mM, respectively. Electron spin resonance analysis suggested that the nitrogen atom of each amine is coordinated to the ferric heme iron. With a concentrated solution of the heme-enzyme complex, however, another species of HA binding appeared, in which the oxygen atom of HA is coordinated to the iron. This species showed an unusual low-spin signal which is similar to that of the ferric hydroperoxide species in the heme Oxygenase Reaction.
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Crystal structure of rat heme Oxygenase-1 in complex with heme.
FEBS letters, 2000Co-Authors: Masakazu Sugishima, Masato Noguchi, Yoshiaki Omata, Yoshimitsu Kakuta, Hiroshi Sakamoto, Keiichi FukuyamaAbstract:Abstract 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 δ- 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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Kinetic isotope effects of peptidylglycine alpha-hydroxylating mono-Oxygenase Reaction.
Biochemical Journal, 1998Co-Authors: Kenichi Takahashi, Tetsuo Onami, Masato NoguchiAbstract:Many bioactive polypeptides or neuropeptides possess a C-terminal alpha-amide group as a critical determinant for their optimal bioactivities. The amide functions are introduced by the sequential actions of peptidylglycine alpha-hydroxylating mono-Oxygenase (PHM; EC 1.14.17.3) and peptidylamidoglycollate lyase (PAL; EC 4.3.2.5) from their glycine-extended precursors. In the present study we examined the kinetic isotope effects of the frog PHM Reaction by competitive and non-competitive approaches. In the competitive approach we employed the double-label tracer method with D-Tyr-[U-14C]Val-Gly, D-Tyr-[3,4-3H]Val-[2,2-2H2]-Gly, and D-Tyr-Val-(R,S)[2-3H]Gly as substrates, and we determined the deuterium and tritium effects on Vmax/Km as 1.625+/-0.041 (mean+/-S. D.) and 2.71+/-0.16 (mean+/-S.D.), respectively. The intrinsic deuterium isotope effect (Dk) on the glycine hydroxylation Reaction was estimated to be 6.5-10.0 (mean 8.1) by the method of Northrop [Northrop (1975) Biochemistry 14, 2644-2651]. In the non-competitive approach with N,N-dimethyl-1,4-phenylenediamine as a reductant, however, the deuterium effect on Vmax (DV) was approximately unity, although the deuterium effect on Vmax/Km (DV/K) was comparable to that obtained by the competitive approach. These results indicated that DV was completely masked by the presence of one or more steps much slower than the glycine hydroxylation step and that DV/K was diminished from Dk by a large forward commitment to catalysis. The addition of PAL, however, increased the apparent DV from 1.0 to 1.2, implying that the product release step was greatly accelerated by PAL. These results suggest that the product release is rate-limiting in the overall PHM Reaction. The large Dk indicated that the glycine hydroxylation catalysed by PHM might proceed in a stepwise mechanism similar to that proposed for the dopamine beta-hydroxylase Reaction [Miller and Klinman (1983) Biochemistry 22, 3091-3096].
Catharina T. Migita - One of the best experts on this subject based on the ideXlab platform.
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Variation of the oxidation state of verdoheme in the heme Oxygenase Reaction
Biochemical and biophysical research communications, 2008Co-Authors: Tomohiko Gohya, Michihiko Sato, Xuhong Zhang, Catharina T. MigitaAbstract:Heme Oxygenase (HO) converts hemin to biliverdin, CO, and iron applying molecular oxygen and electrons. During successive HO Reactions, two intermediates, α-hydroxyhemin and verdoheme, have been generated. Here, oxidation state of the verdoheme-HO complexes is controversial. To clarify this, the heme conversion by soybean and rat HO isoform-1 (GmHO-1 and rHO-1, respectively) was compared both under physiological conditions, with oxygen and NADPH coupled with ferredoxin reductase/ferredoxin for GmHO-1 or with cytochrome P450 reductase for rHO-1, and under a non-physiological condition with hydrogen peroxide. EPR measurements on the hemin-GmHO-1 Reaction with oxygen detected a low-spin ferric intermediate, which was undetectable in the rHO-1 Reaction, suggesting the verdoheme in the six-coordinate ferric state in GmHO-1. Optical absorption measurements on this Reaction indicated that the heme degradation was extremely retarded at verdoheme though this Reaction was not inhibited under high-CO concentrations, unlike the rHO-1 Reaction. On the contrary, the Gm and rHO-1 Reactions with hydrogen peroxide both provided ferric low-spin intermediates though their yields were different. The optical absorption spectra suggested that the ferric and ferrous verdoheme coexisted in Reaction mixtures and were slowly converted to the ferric biliverdin complex. Consequently, in the physiological oxygen Reactions, the verdoheme is found to be stabilized in the ferric state in GmHO-1 probably guided by protein distal residues and in the ferrous state in rHO-1, whereas in the hydrogen peroxide Reactions, hydrogen peroxide or hydroxide coordination stabilizes the ferric state of verdoheme in both HOs.
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o2 and h2o2 dependent verdoheme degradation by heme Oxygenase Reaction mechanisms and potential physiological roles of the dual pathway degradation
Journal of Biological Chemistry, 2005Co-Authors: Toshitaka Matsui, Tadashi Yoshida, Catharina T. Migita, Aya Nakajima, Hiroshi Fujii, Kathryn Mansfield Matera, Masao IkedasaitoAbstract:Heme Oxygenase (HO) catalyzes the catabolism of heme to biliverdin, CO, and a free iron through three successive oxygenation steps. The third oxygenation, oxidative degradation of verdoheme to biliverdin, has been the least understood step despite its importance in regulating HO activity. We have examined in detail the degradation of a synthetic verdoheme IXα complexed with rat HO-1. Our findings include: 1) HO degrades verdoheme through a dual pathway using either O2 or H2O2; 2) the verdoheme reactivity with O2 is the lowest among the three O2 Reactions in the HO catalysis, and the newly found H2O2 pathway is ∼40-fold faster than the O2-dependent verdoheme degradation; 3) both Reactions are initiated by the binding of O2 or H2O2 to allow the first direct observation of degradation intermediates of verdoheme; and 4) Asp140 in HO-1 is critical for the verdoheme degradation regardless of the oxygen source. On the basis of these findings, we propose that the HO enzyme activates O2 and H2O2 on the verdoheme iron with the aid of a nearby water molecule linked with Asp140. These mechanisms are similar to the well established mechanism of the first oxygenation, meso-hydroxylation of heme, and thus, HO can utilize a common architecture to promote the first and third oxygenation steps of the heme catabolism. In addition, our results infer the possible involvement of the H2O2-dependent verdoheme degradation in vivo, and potential roles of the dual pathway Reaction of HO against oxidative stress are proposed.
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Mechanism of heme degradation by heme Oxygenase.
Journal of Inorganic Biochemistry, 2000Co-Authors: Tadashi Yoshida, Catharina T. MigitaAbstract:Abstract Heme Oxygenase catalyzes the three step-wise oxidation of hemin to α-biliverdin, via α- meso -hydroxyhemin, verdoheme, and ferric iron–biliverdin complex. This enzyme is a simple protein which does not have any prosthetic groups. However, heme and its two metabolites, α- meso -hydroxyhemin and verdoheme, combine with the enzyme and activate oxygen during the heme Oxygenase Reaction. In the conversion of hemin to α- meso -hydroxyhemin, the active species of oxygen is Fe-OOH, which self-hydroxylates heme to form α- meso -hydroxyhemin. This step determines the α-specificity of the Reaction. For the formation of verdoheme and liberation of CO from α- meso -hydroxyhemin, oxygen and one reducing equivalent are both required. However, the ferrous iron of the α- meso -hydroxyheme is not involved in the oxygen activation and unactivated oxygen is reacted on the ‘activated’ heme edge of the porphyrin ring. For the conversion of verdoheme to the ferric iron–biliverdin complex, both oxygen and reducing agents are necessary, although the precise mechanism has not been clear. The reduction of iron is required for the release of iron from the ferric iron–biliverdin complex to complete total heme Oxygenase Reaction.
Genhai Zhu - One of the best experts on this subject based on the ideXlab platform.
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Formation of the tight-binding inhibitor, 3-ketoarabinitol-1,5-bisphosphate by ribulose-1,5-bisphosphate carboxylase/Oxygenase is O_2-dependent
Photosynthesis Research, 1998Co-Authors: Genhai Zhu, Richard G Jensen, Hans J. Bohnert, Günter F. WildnerAbstract:Ribulose-1,5-bisphosphate carboxylase/Oxygenase (Rubisco) (EC 4.1.1.39) not only catalyzes carboxylation and oxygenation of ribulose-1,5-bisphosphate (RuBP), but it can also act either as an epimerase or isomerase converting RuBP into xylulose-1,5-bisphosphate (XuBP) or 3-ketoarabinitol-1,5-bisphosphate (KABP), respectively, a process called misfire. XuBP is formed as a result of misprotonation at C3 of the RuBP-enediol. It is released from Rubisco active sites and accumulates in the Reaction mixture. Increasing the amounts of CO_2 or O_2 decreases XuBP production. However, KABP synthesis, which has been proposed to be only a product due to C2 misprotonation of the RuBP-endiol, is dependent upon the presence of O_2. KABP remains tightly bound to Rubisco active sites after its formation, causing the loss of Rubisco activity (‘fallover’). The results suggest that the non-stabilized form of the peroxy-intermediate in the Oxygenase Reaction can be converted in a backReaction to KABP and molecular oxygen. The stabilization of the peroxy-intermediate due to the presence of Mn^2+ instead of Mg^2+ eliminates the formation of KABP.
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simple determination of the co2 o2 specificity of ribulose 1 5 bisphosphate carboxylase Oxygenase by the specific radioactivity of 14c glycerate 3 phosphate
Plant Physiology, 1992Co-Authors: Genhai Zhu, Richard G Jensen, Richard B Hallick, Günter F. WildnerAbstract:A new method is presented for measurement of the CO(2)/O(2) specificity factor of ribulose-1,5-bisphosphate carboxylase/Oxygenase (Rubisco). The [(14)C]3-phosphoglycerate (PGA) from the Rubisco carboxylase Reaction and its dilution by the Rubisco Oxygenase Reaction was monitored by directly measuring the specific radioactivity of PGA. (14)CO(2) fixation with Rubisco occurred under two Reaction conditions: carboxylase with Oxygenase with 40 micromolar CO(2) in O(2)-saturated water and carboxylase only with 160 micromolar CO(2) under N(2). Detection of the specific radioactivity used the amount of PGA as obtained from the peak area, which was determined by pulsed amperometry following separation by high-performance anion exchange chromatography and the radioactive counts of the [(14)C]PGA in the same peak. The specificity factor of Rubisco from spinach (Spinacia oleracea L.) (93 +/- 4), from the green alga Chlamydomonas reinhardtii (66 +/- 1), and from the photosynthetic bacterium Rhodospirillum rubrum (13) were comparable with the published values measured by different methods.
Tadashi Yoshida - One of the best experts on this subject based on the ideXlab platform.
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o2 and h2o2 dependent verdoheme degradation by heme Oxygenase Reaction mechanisms and potential physiological roles of the dual pathway degradation
Journal of Biological Chemistry, 2005Co-Authors: Toshitaka Matsui, Tadashi Yoshida, Catharina T. Migita, Aya Nakajima, Hiroshi Fujii, Kathryn Mansfield Matera, Masao IkedasaitoAbstract:Heme Oxygenase (HO) catalyzes the catabolism of heme to biliverdin, CO, and a free iron through three successive oxygenation steps. The third oxygenation, oxidative degradation of verdoheme to biliverdin, has been the least understood step despite its importance in regulating HO activity. We have examined in detail the degradation of a synthetic verdoheme IXα complexed with rat HO-1. Our findings include: 1) HO degrades verdoheme through a dual pathway using either O2 or H2O2; 2) the verdoheme reactivity with O2 is the lowest among the three O2 Reactions in the HO catalysis, and the newly found H2O2 pathway is ∼40-fold faster than the O2-dependent verdoheme degradation; 3) both Reactions are initiated by the binding of O2 or H2O2 to allow the first direct observation of degradation intermediates of verdoheme; and 4) Asp140 in HO-1 is critical for the verdoheme degradation regardless of the oxygen source. On the basis of these findings, we propose that the HO enzyme activates O2 and H2O2 on the verdoheme iron with the aid of a nearby water molecule linked with Asp140. These mechanisms are similar to the well established mechanism of the first oxygenation, meso-hydroxylation of heme, and thus, HO can utilize a common architecture to promote the first and third oxygenation steps of the heme catabolism. In addition, our results infer the possible involvement of the H2O2-dependent verdoheme degradation in vivo, and potential roles of the dual pathway Reaction of HO against oxidative stress are proposed.
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Mechanism of heme degradation by heme Oxygenase.
Journal of Inorganic Biochemistry, 2000Co-Authors: Tadashi Yoshida, Catharina T. MigitaAbstract:Abstract Heme Oxygenase catalyzes the three step-wise oxidation of hemin to α-biliverdin, via α- meso -hydroxyhemin, verdoheme, and ferric iron–biliverdin complex. This enzyme is a simple protein which does not have any prosthetic groups. However, heme and its two metabolites, α- meso -hydroxyhemin and verdoheme, combine with the enzyme and activate oxygen during the heme Oxygenase Reaction. In the conversion of hemin to α- meso -hydroxyhemin, the active species of oxygen is Fe-OOH, which self-hydroxylates heme to form α- meso -hydroxyhemin. This step determines the α-specificity of the Reaction. For the formation of verdoheme and liberation of CO from α- meso -hydroxyhemin, oxygen and one reducing equivalent are both required. However, the ferrous iron of the α- meso -hydroxyheme is not involved in the oxygen activation and unactivated oxygen is reacted on the ‘activated’ heme edge of the porphyrin ring. For the conversion of verdoheme to the ferric iron–biliverdin complex, both oxygen and reducing agents are necessary, although the precise mechanism has not been clear. The reduction of iron is required for the release of iron from the ferric iron–biliverdin complex to complete total heme Oxygenase Reaction.
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Importance of histidine residue 25 of rat heme Oxygenase for its catalytic activity.
Biochemical and biophysical research communications, 1992Co-Authors: Kazunobu Ishikawa, Michihiko Sato, Mariko Ito, Tadashi YoshidaAbstract:A truncated, soluble, and enzymatically active rat heme Oxygenase lacking its membrane-associative, C-terminal segment was expressed in E. coli strain JM109. The roles of its four histidine residues were examined by determining the enzymatic activities of mutant enzymes in which each of these residues in turn was replaced by alanine. Mutation of histidine residue 25 to alanine resulted in marked decrease in activity for heme breakdown, indicating that this histidine residue has an important role in the heme Oxygenase Reaction.
