Martha E. Sosa Torres and Peter M. H. Kroneck (Guest Editors), Astrid Sigel, Eva Freisinger and Roland K. O. Sigel (Series Editors): Transition metals and sulfur: a strong relationship for life, Vol. 20 of metal ions in life sciences (original) (raw)
Related papers
On the antiquity of metalloenzymes and their substrates in bioenergetics
Many metalloenzymes that inject and extract reducing equivalents at the beginning and the end of electron transport chains involved in chemiosmosis are suggested, through phylogenetic analysis, to have been present in the Last Universal Common Ancestor (LUCA). Their active centres are afne with the structures of minerals presumed to contribute to precipitate membranes produced on the mixing of hydrothermal solutions with the Hadean Ocean ~4 billion years ago. These mineral precipitates consist of transition element sulphides and oxides such as nickelian mackinawite ([Fe > Ni] 2 S 2), a nickel-bearing greigite (~FeSS[Fe 3 NiS 4 ]SSFe), violarite (~NiSS[Fe 2 Ni 2 S 4 ]SSNi), a molybdenum bearing complex (~Mo IV/VI 2 Fe 3 S 0/2− 9) and green rust or fougerite (~[Fe II Fe III (OH) 4 ] + [OH] −). They may be respectively compared with the active centres of Ni–Fe hydrogenase, carbon monoxide dehydrogenase (CODH), acetyl coenzyme-A synthase (ACS), the complex iron–sulphur molybdoenzyme (CISM) superfamily and methane monooxygenase (MMO). With the look of good catalysts – a suggestion that gathers some support from prebiotic hydrothermal experimentation – and sequestered by short peptides, they could be thought of as the original building blocks of proto-enzyme active centres. This convergence of the makeup of the LUCA-metalloenzymes with mineral structure and composition of hydrothermal precipitates adds credence to the alkaline hydrothermal (chemiosmotic) theory for the emergence of life, specically to the possibility that the rst metabolic pathway – the acetyl CoA pathway – was initially driven from either end, reductively from CO 2 to CO and oxidatively and reductively from CH 4 through to a methane thiol group, the two entities assembled with the help of a further thiol on a violarite cluster seques-tered by peptides. By contrast, the organic coenzymes were entirely a product of the rst metabolic pathways. This article is part of a Special Issue entitled: Metals in Bioenergetics and Biomimetics Systems. Published by Elsevier B.V. It is the inorganic elements that bring organic chemistry to life David Garner
Catalysts
A large number of enzymes need a metal ion to express their catalytic activity. Among the different roles that metal ions can play in the catalytic event, the most common are their ability to orient the substrate correctly for the reaction, to exchange electrons in redox reactions, to stabilize negative charges. In many reactions catalyzed by metal ions, they behave like the proton, essentially as Lewis acids but are often more effective than the proton because they can be present at high concentrations at neutral pH. In an attempt to adapt to drastic environmental conditions, enzymes can take advantage of the presence of many metal species in addition to those defined as native and still be active. In fact, today we know enzymes that contain essential bulk, trace, and ultra-trace elements. In this work, we report theoretical results obtained for three different enzymes each of which contains different metal ions, trying to highlight any differences in their working mechanism as a f...
Iron-sulfur proteins: Recent developments in the field
Experientia, 1982
Iron-sulfur clusters in proteins are now recognized as among the main types of electron-transferring groups in biological systems, besides heme and flavins. Recent developments have brought forth a better understanding about the ways the protein environment modulates the potential of the cluster by placing the cluster in a more or less hydrophobic surrounding. Refinement in models, extensive studies on the kinetics of electron transfer (e.g. by measurement of the electronic spin lattice relaxation time) and the introduction of novel spectroscopic methods (EXAFS, magnetic CD and others) in the elucidation of structures in various systems are among the main developments. Other advances include EPR studies of the spatial orientation of Fe-S centers in complex membraneous systems (e.g. in mitochondria) and the recent elucidation of the nature of center X in photosystem I by M6ssbauer-spectroscopy. M6ssbauer studies have also been described on a number of Fe-S proteins (nitrogenase, aconitase, some ferredoxins, etc.) and revealed the existence of novel structures that enlarged the number of known basic units of Fe-S centers. These advances include: 1. the discovery of a novel non-heme Fe-protein (called desulforedoxin) of the rebredoxin type, 2. the elucidation of the nitrogenase Fe-S centers and the nitrogenase cofactor and 3. the discovery of a three-iron cluster in several enzyme s and some ferredoxins. The latter 3-Fe cluster seems capable of being converted into a classical 4-Fe cluster under appropriate conditions, a phenomenon that plays a role in activation-deactivation of some enzymes (e.g. aconitase). It is now recognized that some iron-sulfur clusters may be involved in systems devoided of any oxydation-reduction reaction and may act as sensors of the surrounding redox potential, triggering the activation/deactivation of an enzyme (cf. e.g. aconitase).
Biochemistry, 2003
Metal-and flavin-dependent sulfhydryl oxidases catalyze the generation of disulfide bonds with reduction of oxygen to hydrogen peroxide. The mammalian skin enzyme has been reported to be copper-dependent, but a recent protein sequence shows it belongs to the Quiescin/sulfhydryl oxidase (QSOX) flavoprotein family. This work demonstrates that avian QSOX is not a metalloenzyme, and that copper and zinc ions inhibit the oxidation of reduced pancreatic ribonuclease by the enzyme. Studies with Zn 2+ , as a redox inactive surrogate for copper, show that one Zn 2+ binds to four-electron-reduced QSOX by diverting electrons away from the flavin and into two of the three redox active disulfide bridges in the enzyme. The resulting zinc complex is modestly air-stable, reverting to a spectrum of the native protein with a t 1/2 of 40 min, whereas the four-electron-reduced native QSOX is reoxidized in less than a second under comparable conditions. Using tris(2-carboxyethyl)phosphine hydrochloride (TCEP), an alternate substrate of QSOX that binds Zn 2+ relatively weakly (unlike dithiothreitol), allows rapid inhibition of oxidase activity to be demonstrated at low micromolar metal levels. Zinc binding was followed by rapid-scanning spectrophotometry. Copper also binds the four-electron-reduced form of QSOX with a visible spectrum suggestive of active site occupancy. In addition to interactions with the reduced enzyme, dialysis experiments show that multiple copper and zinc ions can bind to the oxidized enzyme without the perturbation of the flavin spectrum seen earlier. These data suggest that a reinvestigation of the metal content of skin sulfhydryl oxidases is warranted. The redox-modulated binding of zinc to QSOX is considered in light of evidence for a role of zinc-thiolate interactions in redox signaling and zinc mobilization.
Mysteries of metals in metalloenzymes
Accounts of chemical research, 2014
Natural metalloenzymes are often the most proficient catalysts in terms of their activity, selectivity, and ability to operate at mild conditions. However, metalloenzymes are occasionally surprising in their selection of catalytic metals, and in their responses to metal substitution. Indeed, from the isolated standpoint of producing the best catalyst, a chemist designing from first-principles would likely choose a different metal. For example, some enzymes employ a redox active metal where a simple Lewis acid is needed. Such are several hydrolases. In other cases, substitution of a non-native metal leads to radical improvements in reactivity. For example, histone deacetylase 8 naturally operates with Zn(2+) in the active site but becomes much more active with Fe(2+). For β-lactamases, the replacement of the native Zn(2+) with Ni(2+) was suggested to lead to higher activity as predicted computationally. There are also intriguing cases, such as Fe(2+)- and Mn(2+)-dependent ribonucleot...
Journal of Biological Chemistry, 2000
The enzymes 3-deoxy-D-manno-octulosonic acid-8phosphate synthase (KDO8PS) and 3-deoxy-D-arabinoheptulosonic acid-7-phosphate synthase (DAHPS) catalyze analogous condensation reactions between phosphoenolpyruvate and D-arabinose 5-phosphate or D-erythrose 4-phosphate, respectively. While several similarities exist between the two enzymatic reactions, classic studies on the Escherichia coli enzymes have established that DAHPS is a metalloenzyme, whereas KDO8PS has no metal requirement. Here, we demonstrate that KDO8PS from Aquifex aeolicus, representing only the second member of the KDO8PS family to be characterized in detail, is a metalloenzyme. The recombinant KDO8PS, as isolated, displays an absorption band at 505 nm and contains approximately 0.4 and 0.2-0.3 eq of zinc and iron, respectively, per enzyme subunit. EDTA inactivates the enzyme in a time-and concentration-dependent manner and eliminates the absorption at 505 nm. The addition of Cu 2؉ to KDO8PS produces an intense absorption at 375 nm, while neither Co 2؉ nor Ni 2؉ produce such an effect. The EDTA-treated enzyme is reactivated by a wide range of divalent metal ions including Ca 2؉ , Cd 2؉ , Co 2؉ , Cu 2؉ , Fe 2؉ , Mg 2؉ , Mn 2؉ , Ni 2؉ , and Zn 2؉ and is reversibly inhibited by higher concentrations (>1 mM) of certain metals. Analysis of several metal forms of the enzyme by plasma mass spectrometry suggests that the enzyme preferentially binds one, two, or four metal ions per tetramer. These observations strongly suggest that A. aeolicus KDO8PS is a metalloenzyme in vivo and point to a previously unrecognized relationship between the KDO8PS and DAHPS families.
Nitschke 2013 antiquity metalloenzymes BBA Metals first
Many metalloenzymes that inject and extract reducing equivalents at the beginning and the end of electron transport chains involved in chemiosmosis are suggested, through phylogenetic analysis, to have been present in the Last Universal Common Ancestor (LUCA). Their active centres are affine with the structures of minerals presumed to contribute to precipitate membranes produced on the mixing of hydrothermal solutions with the Hadean Ocean~4 billion years ago. These mineral precipitates consist of transition element sulphides and oxides such as nickelian mackinawite ([Fe > Ni] 2 S 2), a nickel-bearing greigite (~FeSS[Fe 3 NiS 4 ]SSFe), violarite (~NiSS[Fe 2 Ni 2 S 4 ]SSNi), a molybdenum bearing complex (~Mo IV/VI 2 Fe 3 S 0/2− 9) and green rust or fougerite (~[Fe II Fe III (OH) 4 ] + [OH] −). They may be respectively compared with the active centres of Ni-Fe hydrogenase, carbon monoxide dehydrogenase (CODH), acetyl coenzyme-A synthase (ACS), the complex iron-sulphur molybdoenzyme (CISM) superfamily and methane monooxygenase (MMO). With the look of good catalystsa suggestion that gathers some support from prebiotic hydrothermal experimentationand sequestered by short peptides, they could be thought of as the original building blocks of proto-enzyme active centres. This convergence of the makeup of the LUCA-metalloenzymes with mineral structure and composition of hydrothermal precipitates adds credence to the alkaline hydrothermal (chemiosmotic) theory for the emergence of life, specifically to the possibility that the first metabolic pathwaythe acetyl CoA pathwaywas initially driven from either end, reductively from CO 2 to CO and oxidatively and reductively from CH 4 through to a methane thiol group, the two entities assembled with the help of a further thiol on a violarite cluster sequestered by peptides. By contrast, the organic coenzymes were entirely a product of the first metabolic pathways. This article is part of a Special Issue entitled: Metals in Bioenergetics and Biomimetics Systems.
Key Bacterial Multi-Centered Metal Enzymes Involved in Nitrate and Sulfate Respiration
Microbial Physiology, 2005
Many essential life processes, such as photosynthesis, respiration, nitrogen fixation, depend on transition metal ions and their ability to catalyze multi-electron redox and hydrolytic transformations. Here we review some recent structural studies on three multi-site metal enzymes involved in respiratory processes which represent important branches within the global cycles of nitrogen and sulfur: (i) the multi-heme enzyme cytochrome c nitrite reductase, (ii) the FAD, FeS-enzyme adenosine-5′-phosphosulfate reductase, and (iii) the siroheme, FeS-enzyme sulfite reductase. Structural information comes from X-ray crystallography and spectroscopical techniques, in special cases catalytically competent intermediates could be trapped and characterized by X-ray crystallography.