Enzymes in facultative anaerobiosis of molluscs—III. Phosphoenolpyruvate carboxykinase and its role in aerobic-anaerobic transition

Mustafa, Tariq; Pw, Hochachka

doi:10.1016/0305-0491(73)90204-6

Cited by 8 publications

(2 citation statements)

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“…On the basis of enzyme activities and kinetics (Holwerda and de Zwaan, 1973;Mustafa and Hochachka, 1973;Holwerda et al, 1981) and from experiments with metabolic inhibitors (Sch6ttler and + 2 glucose + 4 CO2 + 8H---,4 succinate (or propionate + CO2) 3 glucose + 2 CO2---,2 acetate + 4 succinate (or propionate + CO2)"…”

Section: Resultsmentioning

confidence: 99%

Aspects of anaerobic metabolism in Anodonta cygnea L.

Holwerda

Veenhof

1984

Comparative Biochemistry and Physiology Part B: Comparative Bio

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Abstract--1. After 6 days of anoxia A. cygnea had produced 1.0 pmole succinate, 2.7 pmole propionate and 1.7/~mole acetate/g of total soft tissue (wet). In addition, 0.35 #mole glutamate had disappeared. No other changes were detectable.2. Concentrations of anaerobic end products and of amino acids differed from organ to organ. Large portions of all end products produced were present in the fluids within the animal.3. Acetate and propionate were also excreted into the surrounding water. 4. In all tissues examined the activity ratio of pyruvate kinase and phosphoenolpyruvate carboxykinase was high 5. The [PEP]0. 5 of pyruvate kinase was relatively low (0.04-0.05 mM at pH 7.5), and the enzyme is not strongly inhibited at decreased pH or in the presence of alanine.6. Anaerobiosis influences this enzyme by decreasing the activity at low substrate concentration.

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Section: Resultsmentioning

confidence: 99%

Aspects of anaerobic metabolism in Anodonta cygnea L.

Holwerda

Veenhof

1984

Comparative Biochemistry and Physiology Part B: Comparative Bio

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“…The metabolic adaptations to facultative anaerobiosis in bivalves include production of the less toxic alanine and the less soluble succinate salts rather than lactate (Stokes and Awapara, 1968; De Zwaan and Zandee, 1972b). Recently, Hochachka and Mustafa (1973) have demonstrated that anaerobic metabolism in the Pacific oyster is adapted to generate additional substrate level phosphorylation as a-ketoglutarate is shunted into the Krebs cycle (Mustafa and Hochachka, 1973).…”

Section: Discussionmentioning

confidence: 99%

BODY FLUID COMPOSITION AND AERIAL OXYGEN CONSUMPTION IN THE FRESHWATER MUSSEL, LIGUMIA SUBROSTRATA (SAY): EFFECTS OF DEHYDRATION AND ANOXIC STRESS

Dietz

1974

The Biological Bulletin

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The freshwater mussel, Liguinia subrostrata, lives in still water within 50 centimeters of the surface (Murray and Leonard, 1962). These animals will migrate with changes in the water surface level. Occasionally, receding flood waters or drying of the pond leave L. subrostrata exposed to the atmosphere. During this time the valves are closed and some animals will survive for several weeks.Other bivalves have survived emersion over 12 months (Dance, 1958).Epithelial tissues used in gas exchange are permeable to water. When exposed to an atmosphere with high relative humidity, water loss is minimal. However, prolonged exposure to a low relative humidity atmosphere results in significant water loss and concomitant changes in body fluid solute concentrations (Hiscock, 1953).

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External CO₂ levels influence energy yielding metabolic pathways under hypoxia in the leech, Hirudo medicinalis

Hildebrandt

1992

J. Exp. Zool.

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Medicinal leeches, Hirudo medicinalis L., were exposed to hypocapnic (nominal pC02 0.0 kPa) or hypercapnic (pC0, 1.3 kPa) hypoxia (p02 2.0 kPa) for up to 4 days. Changes in blood concentrations and tissue content of organic acids were measured.In the early phase of hypercapnic hypoxia leeches accumulated mainly succinate, and the normally high malate concentrations in blood and tissue were reduced concomitantly. Between 2 and 24 h of hypoxia the animals started to produce propionate which is the major end-product of this type of hypoxia. Only low concentrations of lactate were found in blood and tissue. During the initial phase of hypocapnic hypoxia an accumulation of succinate was also observed, but at a higher rate than during hypercapnic hypoxia. Subsequently, propionate was also produced. Between 24 and 48 h of hypocapnic hypoxia the concentrations of succinate in blood and tissue decreased rapidly and lactate appeared as an end-product of anaerobic metabolism.The results indicate that, in leeches under "environmental" hypoxia, the external concentration of carbon dioxide affects the pathway of carbohydrate metabolism resulting in either succinatelpmpionate production or in lactate accumulation. 0 1992 Wiley-Liss, Inc.Many aquatic animals have to cope with situations of limited oxygen availability in their habitat. To sustain longer periods of severe hypoxia it is essential to maintain energy supply from metabolic pathways which are not dependent on the presence of oxygen. Transition to anaerobic metabolism and, in many cases, a decrease in metabolic rate occur when the oxygen partial pressure of the environment drops below critical values (Zebe and Schottler, '86; Hochachka, '86).In many animals under hypoxic conditions the degradation of glycogen to lactate via the EmbdenMeyerhof-Parnas pathway (anaerobic glycolysis) is the main energy-yielding process. In contrast, especially in those animals which are obligate anaerobes or sustain longer periods of "environmental" hypoxia (e.g., parasitic helminths in the intestine of vertebrates, some molluscs, and annelids), glycogen is degraded to succinate and propionate (Hochachka and Mustafa, '72) which is, in terms of ATP production, a more efficient metabolic pathway than lactate generation (Schottler, '77; Schroff and Zebe, '80).Succinate production in anaerobic annelids requires the carboxylation of phosphoenolpyruvate (PEP) which is catalyzed by phosphoenolpyruvate carboxykinase (PEPCK) (Hoffmann et al., '79). Another enzyme, pyruvate kinase (PK), competes for PEP at this metabolic branchpoint converting PEP to pyruvate, which is a n intermediate metabolite for lactate production. The direction of carbohydrate metabolism a t the level of PEP is determined by the activity ratio of PEPCK to PK as confirmed by the observation that specific inhibition of the PEPCK in hypoxic Arenicola marina resulted in lactate accumulation (Schottler and Wienhausen, '81) although lactate is not a regular end-product of anaerobiosis in this species. Various mechanisms have...

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Enzymes in facultative anaerobiosis of molluscs—III. Phosphoenolpyruvate carboxykinase and its role in aerobic-anaerobic transition

Cited by 8 publications

References 12 publications

Aspects of anaerobic metabolism in Anodonta cygnea L.

Aspects of anaerobic metabolism in Anodonta cygnea L.

BODY FLUID COMPOSITION AND AERIAL OXYGEN CONSUMPTION IN THE FRESHWATER MUSSEL, LIGUMIA SUBROSTRATA (SAY): EFFECTS OF DEHYDRATION AND ANOXIC STRESS

External CO₂ levels influence energy yielding metabolic pathways under hypoxia in the leech, Hirudo medicinalis

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Enzymes in facultative anaerobiosis of molluscs—III. Phosphoenolpyruvate carboxykinase and its role in aerobic-anaerobic transition

Cited by 8 publications

References 12 publications

Aspects of anaerobic metabolism in Anodonta cygnea L.

Aspects of anaerobic metabolism in Anodonta cygnea L.

BODY FLUID COMPOSITION AND AERIAL OXYGEN CONSUMPTION IN THE FRESHWATER MUSSEL, LIGUMIA SUBROSTRATA (SAY): EFFECTS OF DEHYDRATION AND ANOXIC STRESS

External CO2 levels influence energy yielding metabolic pathways under hypoxia in the leech, Hirudo medicinalis

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External CO₂ levels influence energy yielding metabolic pathways under hypoxia in the leech, Hirudo medicinalis