Effect of growth substrate on enzymes of the citric and glyoxylic acid cycles in Thiobacillus novellus

1971 ◽  
Vol 17 (5) ◽  
pp. 617-624 ◽  
Author(s):  
A. Michael Charles
Keyword(s):  
Citric Acid ◽  
High Speed ◽  
Citric Acid Cycle ◽  
Nadh Oxidase ◽  
Specific Activity ◽  
Glyoxylic Acid ◽  
Growth Substrate ◽  
Malic Dehydrogenase ◽  
Aconitate Hydratase ◽  
Acid Cycle

A quantitative study was conducted of enzymes involved in the citric acid cycle and associated systems of the facultative autotroph Thiobacillus novellus grown on five different substrates. Irrespective of the growth substrate the organism possessed complete citric and glyoxylic acid cycles and the specific activity of α-ketoglutarate dehydrogenase was always quite low. Also, the activities of the enzymes of both cycles were usually lowest in extracts from autotrophic cells, and highest in extracts from acetate-grown cells. The three remaining extracts had activities that were between the two extremes with those from glucose-grown cells generally lower than those from pyruvate and succinate. Several exceptions should be noted among these generalizations. For example, the activity of aconitate hydratase and malic dehydrogenase was lowest in extracts from glucose-grown cells while that of isocitric dehydrogenase was lowest in extracts from pyruvate-grown cells. Transhydrogenase activity was virtually absent from extracts of pyruvate- and succinate-grown cells while NADH oxidase, which was identical in these two extracts, was also relatively low. Of interest is the large amount of cytochrome c found in high-speed supernatants. In extracts from autotrophic cells this was about 2.3% of the soluble protein and is suggestive of a significant role being played by the electron-transport system during growth of the organism.

scholarly journals Ubiquinone reduction pattern in pigeon heart mitochondria. Identification of three distinct ubiquinone pools

1985 ◽  
Vol 229 (3) ◽  
pp. 621-629 ◽  
Author(s):  
B M Jørgensen ◽  
H N Rasmussen ◽  
U F Rasmussen
Keyword(s):  
Citric Acid ◽  
Citric Acid Cycle ◽  
Nadh Oxidase ◽  
Heart Mitochondria ◽  
Acid Cycle ◽  
Oxidase System ◽  
Mitochondrial Inner Membrane ◽  
Reducing Conditions ◽  
Endogenous Substrates ◽  
Effect Of Inhibitors

Intact pigeon heart mitochondria showed 10-30% ubiquinone reduction in the absence of substrates. This reduction could not be ascribed to endogenous substrates, as judged by lack of effect of inhibitors and uncouplers and by the very low endogenous respiratory rate. Addition of NADH in the presence of antimycin caused further reduction of about 10% ubiquinone, apparently coupled to the rotenone- and antimycin-sensitive exo-NADH oxidase system [Rasmussen (1969) FEBS Lett. 2, 157-162]. Citric acid cycle substrates reduced most of the remaining ubiquinone in the presence of antimycin; 15-20% of the total ubiquinone content was still in the oxidized form under the most reducing conditions. Three pools of ubiquinone therefore appeared to be present in heart mitochondria: a metabolically inactive pool consisting of reduced as well as oxidized ubiquinone, a pool coupled to oxidation of added (cytoplasmic) NADH, and the well-known pool coupled to citric acid cycle oxidations. Ferricyanide selectively oxidized the ubiquinol reduced by added NADH, indicating that this pool is situated on the outer surface of the mitochondrial inner membrane. Ubiquinone reduction levels were determined with a new method, which is described in detail.

scholarly journals Production of tricarballylic acid by rumen microorganisms and its potential toxicity in ruminant tissue metabolism

1986 ◽  
Vol 56 (1) ◽  
pp. 153-162 ◽  
Author(s):  
James B. Russell ◽  
Neil Forsberg
Keyword(s):  
Citric Acid ◽  
Citric Acid Cycle ◽  
Competitive Inhibitor ◽  
Rumen Microorganisms ◽  
Aconitate Hydratase ◽  
Factors Affecting ◽  
Acid Cycle ◽  
Rat Liver Cells ◽  
High Concentrations

1. Rumen microorganisms convert trans-aconitate to tricarballylate. The following experiments describe factors affecting the yield of tricarballylate, its absorption from the rumen into blood and its effect on mammalian citric acid cycle activity in vitro.2. When mixed rumen microorganisms were incubated in vitro with Timothy hay (Phleum praiense L.) and 6.7 mM-trans-aconitate, 64 % of the trans-aconitate was converted to tricarballylate. Chloroform and nirate treatments inhibited methane production and increased the yield of tricarballylate to 82 and 75% respectively.3. Sheep given gelatin capsules filled with 20 g trans-aconitate absorbed tricarballylate and the plasma concentration ranged from 0.3 to 0.5 mM 9 h after administration. Feeding an additional 40 g potassium chloride had little effect on plasma tricarballylate concentrations. Between 9 and 36 h there was a nearly linear decline in plasma tricarballylate.4. Tricarballylate was a competitive inhibitor of the enzyme, aconitate hydratase (aconitase; EC 4.2.1.3), and the inhibitor constant, KI, was 0.52 mM. This KIvalue was similar to the Michaelis-Menten constant (Km) of the enzyme for citrate.5. When liver slices from sheep were incubated with increasing concentrations of tricarballylate, [I4C]acetate oxidation decreased. However, even at relatively high concentrations (8 mM), oxidation was still greater than 80% of the maximum. Oxidation of [I4C]acetate by isolated rat liver cells was inhibited to a greater extent by tricarballylate. Concentrations as low as 0.5 mM caused a 30% inhibition of citric acid cycle activity.

ENERGY METABOLISM OF PHYCOMYCES BLAKESLEEANUS THE CITRIC ACID CYCLE AND ASSOCIATED AMINO ACIDS

1966 ◽  
Vol 12 (1) ◽  
pp. 1-4 ◽  
Author(s):  
Edwin C. Gangloff
Keyword(s):  
Amino Acids ◽  
Citric Acid ◽  
Energy Metabolism ◽  
Organic Acids ◽  
High Activity ◽  
Citric Acid Cycle ◽  
Specific Activity ◽  
Nitrogen Compounds ◽  
Phycomyces Blakesleeanus ◽  
Acid Cycle

All of the intermediates of the citric acid cycle are shown to be present in the mycelium of 6-day cultures of P. blakesleeanus grown on glucose and on ammonium sulfate, and fed non-radioactive acetate on the fourth and fifth days and acetate-1-C14 on the fifth day of incubation.The concentration of organic acids and certain amino acids, and their specific activity is reported. The high activity of the latter is thought to indicate the presence of a highly labeled pool of nitrogen compounds persisting from the early anabolic reactions after acetate-1-C14 administration.

Oxidative metabolism of bovine spermatozoa

1968 ◽  
Vol 46 (10) ◽  
pp. 1331-1332
Author(s):  
J. F. Masken ◽  
M. L. Hopwood
Keyword(s):  
Oxygen Consumption ◽  
Citric Acid ◽  
Melting Point ◽  
Oxidative Metabolism ◽  
Phosphate Buffer ◽  
Citric Acid Cycle ◽  
Specific Activity ◽  
Acid Cycle ◽  
Bovine Sperm ◽  
Bovine Spermatozoa

Suspensions of washed bovine sperm (phosphate buffer, pH 7.4) were incubated at 37 °C for 1 h with pyruvate-3-14C and in some cases, with oxaloacetate. Oxygen consumption and 14CO2 evolution were measured. Radioactive citrate, malate, fumarate, α-ketoglutarate, and oxaloacetate were found following incubation. The latter two compounds were positively identified by melting-point and specific-activity determinations of their 2,4-dinitrophenylhydrazone derivatives. The results indicate citric acid cycle activity in bull sperm. Oxygen consumption and the evolution of 14CO2 from pyruvate-3-14C tended to decline when oxaloacetate was added to the sperm suspensions.

scholarly journals Control of the citric acid cycle by glyoxylate. The mechanism of inhibition of oxoglutarate dehydrogenase, isocitrate dehydrogenase and aconitate hydratase

1969 ◽  
Vol 114 (3) ◽  
pp. 513-518 ◽  
Author(s):  
A. Adinolfi ◽  
R. Moratti ◽  
S. Olezza ◽  
A. Ruffo
Keyword(s):  
Citric Acid ◽  
Isocitrate Dehydrogenase ◽  
Citric Acid Cycle ◽  
Direct Interaction ◽  
Inhibitory Effect ◽  
Aconitate Hydratase ◽  
Acid Cycle ◽  
Mechanism Of Inhibition ◽  
Oxoglutarate Dehydrogenase ◽  
Thiamin Pyrophosphate

1. The effects of glyoxylate on partially purified preparations of aconitate hydratase, isocitrate dehydrogenase and oxoglutarate dehydrogenase were compared with those of oxalomalate and hydroxyoxoglutarate (obtained by condensation of glyoxylate with oxaloacetate and pyruvate respectively). 2. Glyoxylate (1mm) did not affect aconitate hydratase and isocitrate dehydrogenase, whereas oxalomalate (1mm) inhibited the enzyme activities completely. 3. Glyoxylate (0·025mm) inhibited oxoglutarate dehydrogenase irreversibly, whereas the same concentrations of oxalomalate and hydroxyoxoglutarate were ineffective. This inhibitory effect was prevented if oxoglutarate, pyruvate or oxaloacetate was mixed with the enzyme before the glyoxylate. 4. Incubation of oxoglutarate dehydrogenase with radioactive glyoxylate produced radioactive carbon dioxide; radioactivity was also recovered in the portion of the enzyme identified with thiamin pyrophosphate. 5. The behaviour of glyoxylate in producing multiple inhibitions of the citric acid cycle, either by direct interaction with oxoglutarate dehydrogenase, or by means of its condensation compounds which inhibit aconitate hydratase and isocitrate dehydrogenase, is discussed.

EFFECT OF SERUM GONADOTROPHIN ON DEHYDROGENASES OF THE CITRIC ACID CYCLE IN THE OVARY OF THE RAT

1963 ◽  
Vol 42 (4) ◽  
pp. 480-484 ◽  
Author(s):  
B. Eckstein ◽  
R. Landsberg
Keyword(s):  
Citric Acid ◽  
Citric Acid Cycle ◽  
Age Groups ◽  
Succinic Dehydrogenase ◽  
Immature Rat ◽  
Acid Cycle ◽  
Immature Rats ◽  
Rat Ovary

ABSTRACT The succinic, malic and isocitric dehydrogenases in the ovary of immature and mature, normal and serum gonadotrophin injected rats were examined. The Qo2 of these enzymes were markedly enhanced in the gonadotrophin injected rats of both age groups, except in the case of succinic dehydrogenase in the ovary of the immature rats, where a slight non-significant decrease was noted. It is concluded that in the mature rat ovary, gonadotrophin administration stimulates the activity of all the examined dehydrogenases of the citric acid cycle, whereas in the immature rat ovary, at least the isocitric- and malic dehydrogenases are thus stimulated.

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