Enzymes involved in the metabolism of thiosulfate by Thiobacillus thioparus. I. Survey of enzymes and properties of sulfite : cytochrome c oxidoreductase

1970 ◽  
Vol 48 (3) ◽  
pp. 334-343 ◽  
Author(s):  
Ronald M. Lyric ◽  
Isamu Suzuki
Keyword(s):  
Molecular Weight ◽  
Cytochrome C ◽  
Marked Effect ◽  
Sulfite Oxidase ◽  
Heme Iron ◽  
Free Enzyme ◽  
Reaction Velocity ◽  
Thiobacillus Thioparus ◽  
Non Heme Iron

Enzymes concerned with the oxidation of thiosulfate were investigated in extracts of Thiobacillus thioparus. The organism possessed sulfite oxidase as well as adenosine-5′-phosphosulfate reductase and thiosulfate-oxidizing enzyme. Sulfite oxidase was purified 160-fold and the properties were studied. The enzyme had a molecular weight of 54 000 and one non-heme iron. The pH had a marked effect on reaction velocity and Km for sulfite, and the pK values for free enzyme and enzyme–sulfite complex were determined as 8.9 and 6.2, respectively. Chloride inhibition was noncompetitive and phosphate was uncompetitive with respect to sulfite. In many properties the T. thioparus enzyme was similar to the enzyme isolated from Thiobacillus novellus.

Enzymes involved in the metabolism of thiosulfate by Thiobacillus thioparus. III. Properties of thiosulfate-oxidizing enzyme and proposed pathway of thiosulfate oxidation

1970 ◽  
Vol 48 (3) ◽  
pp. 355-363 ◽  
Author(s):  
Ronald M. Lyric ◽  
Isamu Suzuki
Keyword(s):  
Molecular Weight ◽  
Cytochrome C ◽  
Heme Iron ◽  
Time Dependent ◽  
Strong Inhibitor ◽  
Thiobacillus Thioparus ◽  
Ph Response ◽  
Thiosulfate Oxidation ◽  
Non Heme Iron ◽  
Thiobacillus Neapolitanus

Thiosulfate-oxidizing enzyme was purified from Thiobacillus thioparus extracts 120- to 160-fold and the properties were studied. The enzyme had a molecular weight of 115 000 and contained 2 moles of non-heme iron. Ferricyanide was a much better electron acceptor than cytochrome c, but with cytochrome c the Km for thiosulfate was lowered from 0.1 mM to 5 μM and the pH response of the enzyme changed. Sulfite was a very strong inhibitor destroying 50% of the activity at 5 μM. The inhibition was time-dependent and essentially irreversible. Properties of the T. thioparus enzyme were compared to those of thiosulfate-oxidizing enzyme isolated from Thiobacillus neapolitanus and Ferrobacillus ferrooxidans. A pathway of thiosulfate oxidation is proposed, and metabolic roles of various enzymes studied in T. thioparus are discussed.

The Sulfite Oxidase of Thiobacillus ferrooxidans (Ferrobacillus ferrooxidans)

1971 ◽  
Vol 49 (10) ◽  
pp. 1125-1130 ◽  
Author(s):  
J. Robie Vestal ◽  
D. G. Lundgren
Keyword(s):  
Molecular Weight ◽  
Enzyme Activity ◽  
Cytochrome C ◽  
Energy Production ◽  
Thiobacillus Ferrooxidans ◽  
Sulfite Oxidase ◽  
Electron Acceptors ◽  
Horse Heart Cytochrome ◽  
Thiobacillus Thioparus ◽  
Horse Heart Cytochrome C

The sulfite oxidase (sulfite: cytochrome c oxidoreductase) from sulfur-grown Thiobacillus ferrooxidans was isolated and partially purified, and its properties were studied. The enzyme was purified 7.3-fold and was 75–85% of the protein present. Sulfite oxidase required SO32− for activity, and could use horse heart cytochrome c and ferricyanide as electron acceptors. The molecular weight was 41 500. The enzyme had a Km for sulfite of 0.58 mM with either ferricyanide or cytochrome c as the electron acceptor. The Km for ferricyanide was 0.25 mM. 5′-AMP did not stimulate enzyme activity. Other properties of the enzyme were similar to the enzyme from Thiobacillus thioparus and Thiobacillus novellus. A metabolic scheme of sulfur utilization for energy production in Thiobacillus ferrooxidans is presented.

Enzymes involved in the metabolism of thiosulfate by Thiobacillus thioparus. II. Properties of adenosine-5′-phosphosulfate reductase

1970 ◽  
Vol 48 (3) ◽  
pp. 344-354 ◽  
Author(s):  
Ronald M. Lyric ◽  
Isamu Suzuki
Keyword(s):  
Molecular Weight ◽  
Cytochrome C ◽  
Electron Acceptor ◽  
Desulfovibrio Desulfuricans ◽  
Thiobacillus Denitrificans ◽  
Ph Optimum ◽  
Thiobacillus Thioparus ◽  
Aps Reductase

Adenosine-5′-phosphosulfate (APS) reductase was purified from Thiobacillus thioparus extracts 25- to 46-fold and the properties were studied. The molecular weight was 170 000 and the enzyme had 1 mole of FAD, 8–10 moles of iron, and 4–5 moles of labile sulfide. Cytochrome c as well as ferricyanide served as the electron acceptor. The pH optimum shifted from 7.4 to 9.5 when cytochrome c was used instead of ferricyanide. The Km values for sulfite and AMP were reduced from 2.5 mM and 100 μM to 17 μM and 2.5 μM, respectively, with cytochrome c as electron acceptor. Properties of the T. thioparus enzyme were compared to those of APS reductase isolated from Thiobacillus denitrificans and Desulfovibrio desulfuricans.

Split-soret cytochrome c from desulfovibrio desulfuricans ATCC 27774, a novel protein that contains both heme and non-heme iron centers

1997 ◽  
Vol 67 (1-4) ◽  
pp. 111
Author(s):  
Cristina Costa ◽  
B. Devreese ◽  
J. Van Beeumen ◽  
V. Papaefthymiou ◽  
A. Simopoulos ◽  
...  
Keyword(s):  
Cytochrome C ◽  
Desulfovibrio Desulfuricans ◽  
Heme Iron ◽  
Non Heme Iron ◽  
Novel Protein

MECHANISM OF Fe++-CYTOCROME c REDUCTASE OF FERROBACILLUS FERROOXIDANS

1967 ◽  
Vol 45 (10) ◽  
pp. 1547-1556 ◽  
Author(s):  
George A. Din ◽  
Isamu Suzuki
Keyword(s):  
Cytochrome C ◽  
Kinetic Studies ◽  
Product Inhibition ◽  
Heme Iron ◽  
Non Heme Iron ◽  
Oxidation Reduction ◽  
Dead End ◽  
Ping Pong ◽  
Stable Forms ◽  
Variable Substrate

The mechanism of Fe++-cytochrome c reductase was investigated. Kinetic studies on initial velocity and product inhibition, as well as spectrofluorometric studies, were consistent with a Ping Pong Bi Bi mechanism with two stable forms of enzyme. The Km values for the substrates were found to be 0.59 mM for Fe++ and 0.085 mM for cytochrome c. The inhibition constants for Fe+++ and reduced cytochrome c were 0.137 mM and 0.0135 mM, respectively. The oxidation–reduction of non-heme iron bound to the enzyme protein was implicated as the responsible factor for the oscillation of the enzyme between its two forms. NaCl was a dead-end inhibitor binding the ferrous form of the enzyme, showing an uncompetitive inhibition with Fe++ as a variable substrate.

PARTICULATE DIHYDROOROTATE OXIDASE SYSTEM FROM A PSEUDOMONAD: LINKAGE WITH THE RESPIRATORY CHAIN

1967 ◽  
Vol 45 (9) ◽  
pp. 1283-1294 ◽  
Author(s):  
Richard W. Miller ◽  
Carolyn T. Kerr
Keyword(s):  
Electron Transport ◽  
Cytochrome C ◽  
Respiratory Chain ◽  
Heme Iron ◽  
Primary Site ◽  
Electron Acceptors ◽  
Stopped Flow ◽  
Oxidase System ◽  
Respiratory Inhibitors ◽  
Non Heme Iron

A particulate dihydroorotate oxidase system was prepared from a soil pseudomonad. Components of the respiratory chain participating in electron transport from dihydroorotate to molecular oxygen are bound non-heme iron, ubiquinone, cytochromes b and c, and cytochrome oxidase. Alternate pathways to oxygen are also operative. Inhibition by conventional respiratory inhibitors was incomplete. Dyes and added cytochrome c were readily reduced by dihydroorotate. Pyridine–adenine dinucleotide coenzymes were not reduced by the substrate. However, oxidase activities for these cofactors may have prevented any net reduction. The primary site of reaction with dihydroorotate probably consists of a dehydrogenase which is linked to the respiratory chain and is reactive with various dyes.In the absence of external electron acceptors or inhibitors, 0.5 mole of oxygen was consumed per mole of dihydroorotate oxidized. The anaerobic rate of reduction of bound cytochrome c, as studied by the stopped–flow technique, was slower than the maximum initial rates of orotate production.

Strongly Coupled Redox-Linked Conformational Switching at the Active Site of the Non-Heme Iron-Dependent Dioxygenase, TauD

2019 ◽  
Author(s):  
Christopher John ◽  
Greg M. Swain ◽  
Robert P. Hausinger ◽  
Denis A. Proshlyakov
Keyword(s):  
Active Site ◽  
Structural Model ◽  
Heme Iron ◽  
Chemical Transformations ◽  
Experimental Conditions ◽  
Strongly Coupled ◽  
Non Heme Iron ◽  
Reversible Redox ◽  
Wide Range ◽  
Complex Structural

2-Oxoglutarate (2OG)-dependent dioxygenases catalyze C-H activation while performing a wide range of chemical transformations. In contrast to their heme analogues, non-heme iron centers afford greater structural flexibility with important implications for their diverse catalytic mechanisms. We characterize an <i>in situ</i> structural model of the putative transient ferric intermediate of 2OG:taurine dioxygenase (TauD) by using a combination of spectroelectrochemical and semi-empirical computational methods, demonstrating that the Fe (III/II) transition involves a substantial, fully reversible, redox-linked conformational change at the active site. This rearrangement alters the apparent redox potential of the active site between -127 mV for reduction of the ferric state and 171 mV for oxidation of the ferrous state of the 2OG-Fe-TauD complex. Structural perturbations exhibit limited sensitivity to mediator concentrations and potential pulse duration. Similar changes were observed in the Fe-TauD and taurine-2OG-Fe-TauD complexes, thus attributing the reorganization to the protein moiety rather than the cosubstrates. Redox difference infrared spectra indicate a reorganization of the protein backbone in addition to the involvement of carboxylate and histidine ligands. Quantitative modeling of the transient redox response using two alternative reaction schemes across a variety of experimental conditions strongly supports the proposal for intrinsic protein reorganization as the origin of the experimental observations.

Plant carotenoid cleavage oxygenases: structure–function relationships and role in development and metabolism

2019 ◽  
Vol 19 (1) ◽  
pp. 1-9 ◽  
Author(s):  
Manoj Kumar Dhar ◽  
Sonal Mishra ◽  
Archana Bhat ◽  
Sudha Chib ◽  
Sanjana Kaul
Keyword(s):  
Higher Plants ◽  
Domain Architecture ◽  
Heme Iron ◽  
Critical Assessment ◽  
Protein Family ◽  
Regulatory Mechanisms ◽  
Non Heme Iron ◽  
Functional Aspects ◽  
Functional Understanding ◽  
Signal Production

Abstract A plant communicates within itself and with the outside world by deploying an array of agents that include several attractants by virtue of their color and smell. In this category, the contribution of ‘carotenoids and apocarotenoids’ is very significant. Apocarotenoids, the carotenoid-derived compounds, show wide representation among organisms. Their biosynthesis occurs by oxidative cleavage of carotenoids, a high-value reaction, mediated by carotenoid cleavage oxygenases or carotenoid cleavage dioxygenases (CCDs)—a family of non-heme iron enzymes. Structurally, this protein family displays wide diversity but is limited in its distribution among plants. Functionally, this protein family has been recognized to offer a role in phytohormones, volatiles and signal production. Further, their wide presence and clade-specific functional disparity demands a comprehensive account. This review focuses on the critical assessment of CCDs of higher plants, describing recent progress in their functional aspects and regulatory mechanisms, domain architecture, classification and localization. The work also highlights the relevant discussion for further exploration of this multi-prospective protein family for the betterment of its functional understanding and improvement of crops.

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