Rat liver heme oxygenase. High level expression of a truncated soluble form and nature of the meso-hydroxylating species.

Wilks, Angela; Montellano, Paul R. Ortiz de

doi:10.1016/s0021-9258(18)41536-0

Cited by 239 publications

(234 citation statements)

References 39 publications

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“…Molecular O 2 is bound to the complex as an oxyferrous intermediate that accepts a second electron from NADPH to form a ferric hydroperoxide intermediate (621,624,625). This intermediate hydroxylates the ␣-methine bridge carbon of the heme ring, forming hydroxy-heme (442,592). The ␣-methine bridge carbon then becomes eliminated as CO resulting in the sequential formation of verdoheme and ferribiliverdin-IX␣ complex (BV-Fe III) (236,457,621,625).…”

Section: A Heme Oxygenasesmentioning

confidence: 99%

Heme Oxygenases in Cardiovascular Health and Disease

Ayer

Zarjou

Agarwal

et al. 2016

Physiological Reviews

183

166

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Heme oxygenases are composed of two isozymes, Hmox1 and Hmox2, that catalyze the degradation of heme to carbon monoxide (CO), ferrous iron, and biliverdin, the latter of which is subsequently converted to bilirubin. While initially considered to be waste products, CO and biliverdin/bilirubin have been shown over the last 20 years to modulate key cellular processes, such as inflammation, cell proliferation, and apoptosis, as well as antioxidant defense. This shift in paradigm has led to the importance of heme oxygenases and their products in cell physiology now being well accepted. The identification of the two human cases thus far of heme oxygenase deficiency and the generation of mice deficient in Hmox1 or Hmox2 have reiterated a role for these enzymes in both normal cell function and disease pathogenesis, especially in the context of cardiovascular disease. This review covers the current knowledge on the function of both Hmox1 and Hmox2 at both a cellular and tissue level in the cardiovascular system. Initially, the roles of heme oxygenases in vascular health and the regulation of processes central to vascular diseases are outlined, followed by an evaluation of the role(s) of Hmox1 and Hmox2 in various diseases such as atherosclerosis, intimal hyperplasia, myocardial infarction, and angiogenesis. Finally, the therapeutic potential of heme oxygenases and their products are examined in a cardiovascular disease context, with a focus on how the knowledge we have gained on these enzymes may be capitalized in future clinical studies.

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Section: A Heme Oxygenasesmentioning

confidence: 99%

Heme Oxygenases in Cardiovascular Health and Disease

Ayer

Zarjou

Agarwal

et al. 2016

Physiological Reviews

183

166

View full text Add to dashboard Cite

show abstract

“…In addition, a broad band centered at 680 nm gains intensity for the first 30 minutes following ascorbate addition and then decreases to approximately half its maximal intensity after an additional 30 minutes. Absorbance at this wavelength could be derived from production of an unstable biliverdin product, 40 but further characterization is needed to reach a definitive conclusion. Nevertheless, based upon the UV/Vis Abs data presented here, it is clear that the W67F substitution alters the rate and/or mechanism of heme degradation by IsdG.…”

Section: Resultsmentioning

confidence: 99%

Ruffling is Essential for Staphylococcus aureus IsdG-catalyzed Degradation of Heme to Staphylobilin

Schuelke-Sanchez

Cornetta

Kocian

et al. 2021

Preprint

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Non-canonical heme oxygenases are enzymes that degrade heme to non-biliverdin products within bacterial heme iron acquisition pathways. These enzymes all contain a conserved second-sphere Trp residue that is essential for enzymatic turnover. Previous studies have revealed several important roles for the conserved second-sphere Trp in Staphylococcus aureus IsdG, S. aureus IsdI, and Mycobacterium tuberculosis MhuD. However, a general model for the geometric, electron-ic, and functional role of the second-sphere Trp had not been deduced prior to this work. Here, UV/Vis absorption (Abs) and circular dichroism (CD) spectroscopies were employed to show that the W67F variant of IsdG perturbs the heme substrate conformation without altering the protein secondary structure. In general, it can now be stated that a dynamic equilibrium between “planar” and “ruffled” substrate conformations exists within non-canonical heme oxygenases, and that the second-sphere Trp favors population of the “ruffled” substrate conformation. 1H nuclear magnetic resonance and magnetic CD spectroscopies were used to characterize the electronic structures of IsdG and IsdI variants with different substrate conformational distributions. These data revealed that the “ruffled” substrate conformation promotes partial porphyrin-to-iron electron transfer, which makes the meso carbons of the porphyrin ring susceptible to radical attack. Finally, UV/Vis Abs spectroscopy was utilized to quantify the enzymatic rates, and electrospray ionization mass spec-trometry was used to identify the product distributions, for variants of IsdG with altered substrate conformational distri-butions. In general, the rate of heme monooxygenation to meso-hydroxyheme by non-canonical heme oxygenasess de-pends upon the population of the “ruffled” substrate conformation. Also, the production of staphylobilin or mycobilin by these enzymes is correlated with the population of the “ruffled” substrate conformation, since variants that favor popula-tion of the “planar” substrate conformation yield significant amounts of biliverdin. These data can be understood within the framework of a concerted rearrangement mechanism for the monooxygenation of heme to meso-hydroxyheme by non-canonical heme oxygenases. However, the mechanisms of IsdG/IsdI and MhuD must diverge following this interme-diate in order to generate distinct staphylobilin and mycobilin products, respectively.

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“…Indeed, for 30 μM W67F IsdG and 1 mM sodium ascorbate, a clear 680 nm band grows for the first 115 minutes of the assay before beginning to diminish. Absorbance at this wavelength is likely derived from production of an unstable biliverdin product [40], but further characterization is needed to reach a definitive conclusion. Nevertheless, based upon the UV/Vis Abs data presented here, it is clear that the W67F substitution alters the rate and/or mechanism of heme degradation by IsdG.…”

Section: W67f Isdg Has a Diminished Rate Of Heme Oxygenationmentioning

confidence: 99%

Ruffling is Essential for Staphylococcus aureus IsdG-catalyzed Degradation of Heme to Staphylobilin

Schuelke-Sanchez

Cornetta

Kocian

et al. 2021

Preprint

View full text Add to dashboard Cite

Non-canonical heme oxygenases are enzymes that degrade heme to non-biliverdin products within bacterial heme iron acquisition pathways. These enzymes all contain a conserved second-sphere Trp residue that is essential for enzymatic turnover. Previous studies have revealed several important roles for the conserved second-sphere Trp in Staphylococcus aureus IsdG, S. aureus IsdI, and Mycobacterium tuberculosis MhuD. However, a general model for the geometric, electronic, and functional role of the second-sphere Trp had not been deduced prior to this work. Here, UV/Vis absorption (Abs) and circular dichroism (CD) spectroscopies were employed to show that the W67F variant of IsdG perturbs the heme substrate conformation without altering the protein secondary structure. In general, it can now be stated that a dynamic equilibrium between “planar” and “ruffled” substrate conformations exists within non-canonical heme oxygenases, and that the second-sphere Trp favors population of the “ruffled” substrate conformation. 1H nuclear magnetic resonance and magnetic CD spectroscopies were used to characterize the electronic structures of IsdG and IsdI variants with different substrate conformational distributions. These data revealed that the “ruffled” substrate conformation promotes partial porphyrin-to-iron electron transfer, which makes the meso carbons of the porphyrin ring susceptible to radical attack. Finally, UV/Vis Abs spectroscopy was utilized to quantify the enzymatic rates, and electrospray ionization mass spectrometry was used to identify the product distributions, for variants of IsdG with altered substrate conformational distributions. In general, the rate of heme oxygenation by non-canonical heme oxygenases depends upon the population of the “ruffled” substrate conformation. Also, the production of staphylobilin or mycobilin by these enzymes is correlated with the population of the “ruffled” substrate conformation, since variants that favor population of the “planar” substrate conformation yield significant amounts of biliverdin. These data can be understood within the framework of a concerted rearrangement mechanism for the monooxygenation of heme to meso-hydroxyheme by non-canonical heme oxygenases. However, the mechanisms of IsdG/IsdI and MhuD must diverge following this intermediate in order to generate distinct staphylobilin and mycobilin products, respectively.

show abstract

Rat liver heme oxygenase. High level expression of a truncated soluble form and nature of the meso-hydroxylating species.

Cited by 239 publications

References 39 publications

Heme Oxygenases in Cardiovascular Health and Disease

Heme Oxygenases in Cardiovascular Health and Disease

Ruffling is Essential for Staphylococcus aureus IsdG-catalyzed Degradation of Heme to Staphylobilin

Ruffling is Essential for Staphylococcus aureus IsdG-catalyzed Degradation of Heme to Staphylobilin

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