Why does sulfite reductase employ siroheme?

Brânzanic, Adrian M.V.; Ryde, Ulf; Silaghi-Dumitrescu, Radu

doi:10.1039/c9cc05271b

Cited by 17 publications

(13 citation statements)

References 25 publications

(14 reference statements)

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“…The prosthetic group assists in the 6-electron reduction of both sulphite and nitrite to allow their incorporation into biological systems at the level of sulphide and ammonia. It has been suggested that siroheme, in preference to heme, allows a more direct charge transfer route to the active center of these enzymes during the catalytic cycle (14). In contrast, heme d1, which like siroheme is not a heme but a dioxo-isobacteriochlorin, is only utilized by one enzyme, a dissimilatory nitrite reductase called cytochrome cd1.…”

Section: Chlsmentioning

confidence: 99%

Biosynthesis of the modified tetrapyrroles—the pigments of life

Bryant

Hunter

Warren

2020

Journal of Biological Chemistry

188

164

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Modified tetrapyrroles are large macrocyclic compounds, consisting of diverse conjugation and metal chelation systems and imparting an array of colors to the biological structures that contain them. Tetrapyrroles represent some of the most complex small molecules synthesized by cells and are involved in many essential processes that are fundamental to life on Earth, including photosynthesis, respiration, and catalysis. These molecules are all derived from a common template through a series of enzyme-mediated transformations that alter the oxidation state of the macrocycle and also modify its size, its side-chain composition, and the nature of the centrally chelated metal ion. The different modified tetrapyrroles include chlorophylls, hemes, siroheme, corrins (including vitamin B12), coenzyme F430, heme d1, and bilins. After nearly a century of study, almost all of the more than 90 different enzymes that synthesize this family of compounds are now known, and expression of reconstructed operons in heterologous hosts has confirmed that most pathways are complete. Aside from the highly diverse nature of the chemical reactions catalyzed, an interesting aspect of comparative biochemistry is to see how different enzymes and even entire pathways have evolved to perform alternative chemical reactions to produce the same end products in the presence and absence of oxygen. Although there is still much to learn, our current understanding of tetrapyrrole biogenesis represents a remarkable biochemical milestone that is summarized in this review.

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Section: Chlsmentioning

confidence: 99%

Biosynthesis of the modified tetrapyrroles—the pigments of life

Bryant

Hunter

Warren

2020

Journal of Biological Chemistry

188

164

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“…The first bears the so-called siroheme, structurally similar to the isobacteriochlorin of F430 cofactor, whose proximal cysteine is bridged to a [4Fe-4S] cluster. The mutual interplay between the two cofactors in SiRs plays a key role in delivering the six electrons needed to convert sulfite to hydrogen sufide [89,90]. The second, also known as Cyt cd1, bears a unique tetrapyrrole ring called heme d1, which shares the same starting scaffold of siroheme [91].…”

Section: Figmentioning

confidence: 99%

Mimochrome, a metalloporphyrin‐based catalytic Swiss knife†

Leone

Chino

Nastri

et al. 2020

Biotech and App Biochem

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Over the years, mimochromes, a class of miniaturized porphyrin‐based metalloproteins, have proven to be reliable but still versatile scaffolds. After two decades from their birth, we retrospectively review our work in mimochrome design and engineering, which allowed us developing functional models. They act as electron‐transfer miniproteins or more elaborate artificial metalloenzymes, endowed with peroxidase, peroxygenase, and hydrogenase activities. Mimochromes represent simple yet functional synthetic models that respond to metal ion replacement and noncovalent modulation of the environment, similarly to natural heme‐proteins. More recently, we have demonstrated that the most active analogue retains its functionality when immobilized on nanomaterials and surfaces, thus affording bioconjugates, useful in sensing and catalysis. This review also briefly summarizes the most important contributions to heme‐protein design from leading groups in the field.

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“…The roles of the distal lysine and arginine residues (Figure E) include binding and orientation of the substrate and transfer of protons to the catalytic site . In addition to the distal residues there is a Fe 4 S 4 cubane bridged to the cluster which provides electrons to the active site, which may achieve the transformation in three 2e – steps. − The same siroheme active site is found in assimilatory nitrite reductases which reduce NO 2 – to NH 4 + . The cytochrome cd 1 nitrite reductase, on the other hand, does not possess the Fe 4 S 4 cluster and uses heme d 1 cofactor and can reduce NO 2 – to NO and not further .…”

Section: Introductionmentioning

confidence: 99%

Second Sphere Effects on Oxygen Reduction and Peroxide Activation by Mononuclear Iron Porphyrins and Related Systems

2022

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Activation and reduction of O2 and H2O2 by synthetic and biosynthetic iron porphyrin models have proved to be a versatile platform for evaluating second-sphere effects deemed important in naturally occurring heme active sites. Advances in synthetic techniques have made it possible to install different functional groups around the porphyrin ligand, recreating artificial analogues of the proximal and distal sites encountered in the heme proteins. Using judicious choices of these substituents, several of the elegant second-sphere effects that are proposed to be important in the reactivity of key heme proteins have been evaluated under controlled environments, adding fundamental insight into the roles played by these weak interactions in nature. This review presents a detailed description of these efforts and how these have not only demystified these second-sphere effects but also how the knowledge obtained resulted in functional mimics of these heme enzymes.

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Why does sulfite reductase employ siroheme?

Abstract: As opposed to heme, siroheme inhibits the charge transfer from the cubane via direct routes.

Cited by 17 publications

References 25 publications

Biosynthesis of the modified tetrapyrroles—the pigments of life

Biosynthesis of the modified tetrapyrroles—the pigments of life

Mimochrome, a metalloporphyrin‐based catalytic Swiss knife†

Second Sphere Effects on Oxygen Reduction and Peroxide Activation by Mononuclear Iron Porphyrins and Related Systems

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