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.

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.

Nitrate-reductase electron-transport cofactors in Veillonella alcalescens

1977 ◽  
Vol 23 (11) ◽  
pp. 1562-1567 ◽  
Author(s):  
K. L. Ruoff ◽  
E. A. Delwiche
Keyword(s):  
Electron Transport ◽  
Nitrate Reductase ◽  
Growth Medium ◽  
Doubling Time ◽  
Growth Yield ◽  
Heme Iron ◽  
Deficient Mutant ◽  
Non Heme Iron ◽  
Reducing Activity

Studies on the effects of inhibitors of the nitrate-reducing activity of Veillonella alcalescens extracts suggest the participation of a naphthoquinone, a b-type cytochrome, and non-heme iron in electron transport to nitrate. A nitrate-reductase-deficient mutant displayed a longer doubling time and a decreased molar growth yield on nitrate media. This mutant was phenotypically restored by the addition of molybdate to the growth medium, giving evidence for the functioning of molybdenum in the nitrate-reductase enzyme of V. alcalescens.

scholarly journals Electron Transport in a Dioxygenase-Ferredoxin Complex: Long Range Charge Coupling between the Rieske and Non-Heme Iron Center

PLoS ONE ◽  
2016 ◽  
Vol 11 (9) ◽  
pp. e0162031 ◽  
Author(s):  
Wayne K. Dawson ◽  
Ryota Jono ◽  
Tohru Terada ◽  
Kentaro Shimizu
Keyword(s):  
Electron Transport ◽  
Long Range ◽  
Heme Iron ◽  
Non Heme Iron ◽  
Iron Center

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.

scholarly journals AN ELECTRON-TRANSPORT SYSTEM ASSOCIATED WITH THE OUTER MEMBRANE OF LIVER MITOCHONDRIA

1967 ◽  
Vol 32 (2) ◽  
pp. 415-438 ◽  
Author(s):  
Gian Luigi Sottocasa ◽  
Bo Kuylenstierna ◽  
Lars Ernster ◽  
Anders Bergstrand
Keyword(s):  
Electron Transport ◽  
Cytochrome C ◽  
Outer Membrane ◽  
Respiratory Chain ◽  
Transport System ◽  
Cytochrome B5 ◽  
Liver Mitochondria ◽  
Electron Transport System ◽  
Cytochrome C Reductase ◽  
Nadh Cytochrome

Preparations of rat-liver mitochondria catalyze the oxidation of exogenous NADH by added cytochrome c or ferricyanide by a reaction that is insensitive to the respiratory chain inhibitors, antimycin A, amytal, and rotenone, and is not coupled to phosphorylation. Experiments with tritiated NADH are described which demonstrate that this "external" pathway of NADH oxidation resembles stereochemically the NADH-cytochrome c reductase system of liver microsomes, and differs from the respiratory chain-linked NADH dehydrogenase. Enzyme distributation data are presented which substantiate the conclusion that microsomal contamination cannot account for the rotenone-insensitive NADH-cytochrome c reductase activity observed with the mitochondria. A procedure is developed, based on swelling and shrinking of the mitochondria followed by sonication and density gradient centrifugation, which permits the separation of two particulate subfractions, one containing the bulk of the respiratory chain components, and the other the bulk of the rotenone-insensitive NADH-cytochrome c reductase system. Morphological evidence supports the conclusion that the former subfraction consists of mitochondria devoid of outer membrane, and that the latter represents derivatives of the outer membrane. The data indicate that the electron-transport system associated with the mitochondrial outer membrane involves catalytic components similar to, or identical with, the microsomal NADH-cytochrome b5 reductase and cytochrome b5.

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

scholarly journals The Respiratory Chain of Beetroot Mitochondria

1960 ◽  
Vol 13 (2) ◽  
pp. 109 ◽  
Author(s):  
JT Wiskich ◽  
RK Morton ◽  
RN Robertson
Keyword(s):  
Cytochrome C ◽  
Absorption Band ◽  
Beta Vulgaris ◽  
Respiratory Chain ◽  
Electron Acceptors ◽  
Root Tissue ◽  
Absorption Bands ◽  
Isolated Mitochondria ◽  
Ferrocytochrome C ◽  
Ferricytochrome C

Mitochondria were isolated from root tissue of red beetroot (Beta vulgaris L.) and the components of the respiratory chain for oxidation of succinate and of reduced diphosphopyridine nucleotide (DPNH) were studied. Succinate, DPNH, ferrocytochrome c, and malate were used as substrates, and 2,6-dichlorophenolindophenol, ferricytochrome c, and oxygen as hydrogen (electron) acceptors. DPNH was oxidized without addition of cytochrome c and malate without addition of DPN. These observations suggest that the respiratory chain was retained intact in the isolated mitochondria. Cytochromes b, C1. and c were identified spectroscopically by the positions of their characteristic ex-absorption bands. The very small amount of cytochrome c present may indicate some loss of this component during isolation of the mitochondria. An absorption band near 600 mp' was attributed to cytochromes (a+a3).

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