The oxidation of tricarboxylic acid cycle intermediates, with particular reference to isocitrate, by intact mitochondria isolated from the liver of the American eel, Anguilla rostrata LeSueur

Moon, Thomas W.; Ouellet, Georges

doi:10.1016/0003-9861(79)90370-9

Cited by 24 publications

(9 citation statements)

References 26 publications

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“…The present study, by documenting NAD +-IDH activity in trout and eel tissues, suggests that there is no need to propose an altered route of isocitrate oxidation in fish; the tricarboxylic acid cycle, as seen in other animals, is complete. However, the distribution of NADP*-IDH in eel liver is intriguing: mitochondrial NADP *-IDH activity exceeds cytoplasmic activity by 3-fold, exactly the opposite to that reported in rat liver (Moon and Ouellet 1979). The adaptive significance of this deserves further attention.…”

Section: Discussionmentioning

confidence: 78%

“…These ratios are considerably higher than equivalent values for other vertebrate species (Alp et al 1976) and this, plus the earlier inability to detect NAD+-IDH in fish liver (Moon and Hochachka 1971;Moon and Ouellet 1979), lead to the initial proposal that the role of NAD+-IDH in the tricarboxylic acid cycle was replaced in fish tissues by mitochondrial NADP +-IDH. The present study, by documenting NAD +-IDH activity in trout and eel tissues, suggests that there is no need to propose an altered route of isocitrate oxidation in fish; the tricarboxylic acid cycle, as seen in other animals, is complete.…”

Section: Discussionmentioning

confidence: 99%

“…The conflicting reports on the presence and absence of NAD+-IDH in tissues of fish (Moon and Hochachka 1971;Moon and Ouellet 1979;Alp et al 1976;Mourika 1983;McCormack and Denton 1981) may well be explained by the inherent instability of the enzyme. The present study demonstrates the presence of NAD+-IDH in several tissues of two species of fish.…”

Section: Discussionmentioning

confidence: 99%

“…It is surprising, therefore, to find occasional claims that this key enzyme is missing. Several workers have attempted to measure the activity of this enzyme in tissues of fish with little success (Moon and Hochachka 1971;Moon and Ouellet 1979). Moon and Ouellet (1979) found that isolated mitochondria from liver of the eel Anguilla rostrata could oxidize added isocitrate and possessed NADP+-linked isocitrate dehydrogenase (EC 1.1.1.42) (NADP+-IDH) as well as an active NADPH:NAD transhydrogenase (EC 1.6.1.1).…”

Section: Introductionmentioning

confidence: 99%

“…Several workers have attempted to measure the activity of this enzyme in tissues of fish with little success (Moon and Hochachka 1971;Moon and Ouellet 1979). Moon and Ouellet (1979) found that isolated mitochondria from liver of the eel Anguilla rostrata could oxidize added isocitrate and possessed NADP+-linked isocitrate dehydrogenase (EC 1.1.1.42) (NADP+-IDH) as well as an active NADPH:NAD transhydrogenase (EC 1.6.1.1). These authors concluded, therefore, that the oxidation of isocitrate in mitochondria from eel liver probably proceeded via the NADP+-IDH and then electrons were transferred to NAD + by the transhydrogenase for entry into the normal electron transfer system.…”

Section: Introductionmentioning

confidence: 99%

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NAD+-linked isocitrate dehydrogenase in fish tissues

Storey

Fields

1988

Fish Physiol Biochem

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NAD(+)-linked isocitrate dehydrogenase was found in the brain, heart, gills, kidney, liver and muscle of trout, and in the liver and muscle of eel. A complex homogenization buffer containing 1 mM ADP, 5 mM MgSO4, 5 mM citrate and 40% glycerol is required for retrieval of significant amounts of stable enzyme. The highest activities were found in brain of trout and the lowest in white muscle of trout and eel. The enzyme was partially purified from frozen trout heart to a final activity of 0.04 μM/min/mg protein, and the kinetic properties of this partially purified enzyme were studied. The enzyme requires either Mn(2+) or Mg(2+) for activity, higher activities being observed with Mn(2+). Saturation kinetics for DL-isocitrate were sigmoidal, apparent S0·5=8.2±0.6 mM and nH=1.8±0.2, in the absence of ADP, changing to hyperbolic, apparent S0·5=1.4±0.3 mM and nH=1.0, with 1 mM ADP added. Citrate and Ca(2+) were found to activate the enzyme to a small extent. NADH strongly inhibited the enzyme, I50=3.7±0.5 μM. ATP was also found to be an inhibitor, I50=7.2±1.4 mM. These properties are consistent with the role of the enzyme as a major control site of the tricarboxylic acid cycle.

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Section: Discussionmentioning

confidence: 78%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

NAD+-linked isocitrate dehydrogenase in fish tissues

Storey

Fields

1988

Fish Physiol Biochem

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Oxidation of amino acids, Krebs cycle intermediates, fatty acids and ketone bodies by Raja erinacea liver mitochondria

1986

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The oxidation of amino acids, Krebs cycle intermediates, fatty acids and ketone bodies was examined in a well-coupled mitochondria1 preparation from the liver of the little skate, Raja erinaceu Glutamate was the preferred amino acid on the basis of both the respiratory control ratio (RCR; 7.97 0.60 SE) and the state 3 rate (12.50 (+ 1.16 SE) nmoles 0 min (mg protein-'). Other amino acids, including sarcosine and 0-alanine, were oxidized at less than one third the rate of glutamate with RCRs less than 4. Oxidation of ornithine and arginine was not detected. Of the Krebs cycle intermediates tested, isocitrate had the best RCR and state 3 rate. Malate enhanced the oxidation of tricarboxylic acids (isocitrate and citrate) and aketoglutarate, probably by stimulation of transport into the mitochondria. Oxaloacetate and succinyl CoA were not oxidized at detectable rates. Pyruvate oxidation was low, even at high concentrations (10 mM). Fatty acids (as carnitine esters) were oxidized at high rates, especially hexanoyl (C-6), octanoyl (C-€9, decanoyl (C-101, lauroyl (C-121, and myristoyl (C-14) carnitine. Acetoacetate oxidation was not detected, but high rates of oxygen consumption were observed in response to 1 mM 0-hydroxybutyrate. Oxidation of this ketone body was malonate-sensitive, although 14C02 production from 3 (14C)-p-hydroxybutyrate was minimal, indicating that ketone body carbon was not entering the Krebs cycle. The malonate sensitivity of the oxidation process was due to direct inhibition of 0-hydroxybutyrate dehydrogenase (150 for malonate = 0.558 (k 0.031 SE) mM). The liver of this skate appears to be well suited to utilize fatty acids rather than ketone bodies or carbohydrate.Interest in the intermediary metabolism of skates has largely been confined to amino acid metabolism in relation to cell volume regulation. Skates maintain high intracellular levels of 0-alanine (BALA) and sarcosine.

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Cyanide detoxification in the mudskipper, Boleophthalmus boddaerti

Chew

1992

J. Exp. Zool.

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The tolerance of the mudskipper, Boleophthalmus boddaerti, to cyanide is higher than those of other fishes reported elsewhere. The 24 h, 48 h, and 96 h LC50 for B. boddaerti were 0.37 mg HCN/liter, 0.34 mg HCNiliter, and 0.29 mg HCN/liter, respectively. The tolerance of B. boddaerti to cyanide does not involve a reduction of metabolic rate or a n enhanced anaerobic metabolism, or a cyanide-insensitive respiratory pathway. Instead, it is a result of the presence of a surplus of cytochrome oxidase and inducible cyanide-detoxifying mechanisms in this mudskipper. Although cytochrome oxidase activities in the various tissues of the fish exposed to 0.23 mg HCN/liter were inhibited by more than 50%, no reduction in the 0 2 consumption rate was observed. B. boddaerti could detoxify cyanide to thiocyanate. The activity of rhodanese in the liver extract of fish exposed to cyanide increased significantly compared to that of the control. The activities of cysteine aminotransferase (CAT) and 3-mercaptopyruvate sulfurtransferase (MPST) in the extracts from the liver and the muscle of B. boddaerti exposed to cyanide also increased significantly compared to those of the control fish. Glutamate formed in the reaction catalyzed by CAT could undergo transamination leading to the accumulation of aspartate in the muscle of the fish exposed to cyanide.Cyanide is a highly toxic compound. It binds to the heme of cytochrome c oxidase in place of molecular oxygen and causes the immediate, although reversible, inhibition of the electron transport chain in aerobic respiration. Preliminary experiments performed in the authors' laboratory revealed that the mudskipper, Boleophthalmus boddaerti, had a greater cyanide tolerance than other fishes. Mudskippers are goboid fishes that inhabit and build burrows on mudflats in estuaries. At low tide, B. boddaerti moves on the mudflats and enters the water occasionally. When the tide rises, it retreats into the hypoxic, if not anoxic, burrows (Gordon et al., '78) and remains submerged until the tide ebbs. The main objectives of these studies were therefore to establish the median lethal concentration (LC50) of cyanide for B. boddaerti and to examine if its high cyanide tolerance was related to its capacity to survive in the absence of O2 in its natural environment. The possibilities of the existence of c yanide-insensitive respiration and cyanide-detoxifying mechanisms in this fish were also examined. MATERIALS AND METHODS Collection and maintenance of B. boddaertiB. boddaerti (6-22 g body weight) were collected along the estuarine canal at Pasir Ris, Singapore. No attempt was made to separate the sexes. They were maintained in 50% seawater (SW; 15%0 salin-0 1992 WILEY-LISS, INC. ity) in small aquaria at 25°C. The aquaria were tilted slightly, so that the water covered only approximately half of the bottom surface of each tank. Water was changed daily and the fish were fed with Goldfish & Staple Flake@ (Everyday Co., Singapore) everyday.Determination of LCs0 o f cyanide for B. boddaerti Groups...

show abstract

The oxidation of tricarboxylic acid cycle intermediates, with particular reference to isocitrate, by intact mitochondria isolated from the liver of the American eel, Anguilla rostrata LeSueur

Cited by 24 publications

References 26 publications

NAD+-linked isocitrate dehydrogenase in fish tissues

NAD+-linked isocitrate dehydrogenase in fish tissues

Oxidation of amino acids, Krebs cycle intermediates, fatty acids and ketone bodies by Raja erinacea liver mitochondria

Cyanide detoxification in the mudskipper, Boleophthalmus boddaerti

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