Multiple Forms of Enzymes

Pevzner, Leonid Z.

doi:10.1007/978-1-4899-1881-9_19

Cited by 11 publications

(3 citation statements)

References 207 publications

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“…The LDH-5 isozyme is predominantly found in lactate-producing tissues, while the LDH-l isozyme is active in aerobic tissues (e.g., the heart) (Cahn et aI., 1962;Markert et a!., 1975). It has been proposed (Cahn et a!., 1962) and generally accepted (Pevzner, 1983) that the LDH-l isoform is better de signed to oxidize lactate to pyruvate, while the LDH-5 isoform preferentially converts pyruvate to lactate (Cahn et aI., 1962).…”

Section: Selective Distribution Of Lactate Dehydrogenase Isoenzymesmentioning

confidence: 99%

Selective Distribution of Lactate Dehydrogenase Isoenzymes in Neurons and Astrocytes of Human Brain

Bittar

Charnay

Pellerin³

et al. 1996

J Cereb Blood Flow Metab

373

277

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In vertebrates, the interconversion of lactate and pyruvate is catalyzed by the enzyme lactate dehydrogenase. Two distinct subunits combine to form the five tetrameric isoenzymes of lactate dehydrogenase. The LDH-5 subunit (muscle type) has higher maximal velocity (Vmax) and is present in glycolytic tissues, favoring the formation of lactate from pyruvate. The LDH-1 subunit (heart type) is inhibited by pyruvate and therefore preferentially drives the reaction toward the production of pyruvate. There is mounting evidence indicating that during activation the brain resorts to the transient glycolytic processing of glucose. Indeed, transient lactate formation during physiological stimulation has been shown by 1H-magnetic resonance spectroscopy. However, since whole-brain arteriovenous studies under basal conditions indicate a virtually complete oxidation of glucose, the vast proportion of the lactate transiently formed during activation is likely to be oxidized. These in vivo data suggest that lactate may be formed in certain cells and oxidized in others. We therefore set out to determine whether the two isoforms of lactate dehydrogenase are localized to selective cell types in the human brain. We report here the production and characterization of two rat antisera, specific for the LDH-5 and LDH-1 subunits of lactate dehydrogenase, respectively. Immunohistochemical, immunodot, and western-blot analyses show that these antisera specifically recognize their homologous antigens. Immunohistochemistry on 10 control cases demonstrated a differential cellular distribution between both subunits in the hippocampus and occipital cortex: neurons are exclusively stained with the anti-LDH1 subunit while astrocytes are stained by both antibodies. These observations support the notion of a regulated lactate flux between astrocytes and neurons.

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Section: Selective Distribution Of Lactate Dehydrogenase Isoenzymesmentioning

confidence: 99%

Selective Distribution of Lactate Dehydrogenase Isoenzymes in Neurons and Astrocytes of Human Brain

Bittar

Charnay

Pellerin³

et al. 1996

J Cereb Blood Flow Metab

373

277

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“…It is well established that the relative distribution of LDH isoenzymes is tissue specific [32,33]. The LDH-4 isoform is specific to kidney and preferentially converts pyruvate to lactate, an indication of anaerobic metabolism [34].…”

Section: Nadh/nadmentioning

confidence: 99%

Ethanol‐induced redox imbalance in rat kidneys

Nechifor

Dinu

2010

J Biochem & Molecular Tox

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This study reports the effects of long-term ethanol consumption on kidney redox status, in terms of enzymatic mechanisms involved in regulating the cytosolic [NADH]/[NAD(+) ] balance. Wistar rats were treated with ethanol (2 g/kg body weight/24 h) via intragastric intubation for 10 and 30 weeks, respectively. Ethanol administration induced an enhancement of alcohol dehydrogenase activities and affected the capacity of the kidney to prevent NADH accumulation in the cytosol. After 10 weeks, the excess of NADH was balanced by increased activities of malate dehydrogenase and aspartate transaminase. In the event of a longer period of ethanol intake, the kidney was not able to balance the NADH excess, even though an increase in malate dehydrogenase, lactate dehydrogenase, aspartate transaminase, and alanine transaminase activities was noted. The electrophoretic analysis of alcohol dehydrogenase, lactate dehydrogenase, and malate dehydrogenase isoforms revealed differences between control and ethanol-treated animals. The results suggest that rat kidneys have a multicomponent metabolic response to the same daily dose of ethanol that functions to maintain the redox status and which varies with the length of the administration period.

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“…Owing to the pattern of lactate dehydrogenase isoenzymes in the perinatal period, lactate production may be less susceptible to substrate inhibition than in adult brain (Bonavita et al, 1964;Kaplan et al, 1968;Pevzner, 1983). Na+, K+-ATPase (which is thought to drive Na+/ Hf exchange) and HC03-/C1exchange activity may be low enough in immature brain (Bertoni and Siegel, 1978;Vernadakis, 1982;Woodbury et al, 1974; Kimelberg and Bourke, 1982) to affect p H regulation by this mechanism.…”

mentioning

confidence: 99%

Acid Homeostasis Following Partial Ischemia in Neonatal Brain Measured In Vivo by ³¹P and ¹H Nuclear Magnetic Resonance Spectroscopy

Corbett¹,

Laptook²

1990

Journal of Neurochemistry

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The purpose of this study was to investigate neonatal brain energy metabolism, acid, and lactate homeostasis in the period immediately following partial ischemia. Changes in brain buffering capacity were quantified by measuring mean intracellular brain pH, calculated from the chemical shift of Pi, in response to identical episodes of hypercarbia before and after ischemia. In addition, the relationship between brain buffer base deficit and intracellular pH was compared during and following ischemia. Thus, in vivo 31P and 1H nuclear magnetic resonance spectra were obtained from the brains of seven newborn piglets exposed to sequential episodes of hypercarbia, partial ischemia, and a second episode of hypercarbia in the postischemic recovery period. For the first episode of hypercarbia, brain buffering was similar to values reported for adult animals of other species (percentage pH regulation = 54 +/- 16%). During ischemia, the brain base deficit per unit change in pH was -19 +/- 5 mM/pH unit, which is similar to values reported for adult rats. By 20-35 min postischemia, brain acidosis partly resolved in spite of a net increase in lactate concentration. Therefore, the consumption of lactate could not explain acid homeostasis in the first 35 min following ischemia. We conclude that H+/HCO3- or other proton equivalent translocation mechanisms must be sufficiently developed in piglet brain to support acid regulation. This is surprising, because a substantial body of evidence implies these processes would be less active in immature brain. The second episode of hypercarbia, from 35 to 65 min postischemia, resulted in a smaller decrease in brain pH compared with the first episode, a result indicating an increase in brain buffering capacity (percentage pH regulation = 79 +/- 29%). This was associated with a parallel decrease in brain lactate content, and therefore acid regulation could be attributed to either continued ion translocation or the consumption of lactate. A mild decrease in brain pH and content of energy metabolites was observed, a finding suggesting that the metabolic consequences of severe postischemic hypercarbia are neither particularly dangerous or beneficial.

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Multiple Forms of Enzymes

Cited by 11 publications

References 207 publications

Selective Distribution of Lactate Dehydrogenase Isoenzymes in Neurons and Astrocytes of Human Brain

Selective Distribution of Lactate Dehydrogenase Isoenzymes in Neurons and Astrocytes of Human Brain

Ethanol‐induced redox imbalance in rat kidneys

Acid Homeostasis Following Partial Ischemia in Neonatal Brain Measured In Vivo by ³¹P and ¹H Nuclear Magnetic Resonance Spectroscopy

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Multiple Forms of Enzymes

Cited by 11 publications

References 207 publications

Selective Distribution of Lactate Dehydrogenase Isoenzymes in Neurons and Astrocytes of Human Brain

Selective Distribution of Lactate Dehydrogenase Isoenzymes in Neurons and Astrocytes of Human Brain

Ethanol‐induced redox imbalance in rat kidneys

Acid Homeostasis Following Partial Ischemia in Neonatal Brain Measured In Vivo by 31P and 1H Nuclear Magnetic Resonance Spectroscopy

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Product

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Acid Homeostasis Following Partial Ischemia in Neonatal Brain Measured In Vivo by ³¹P and ¹H Nuclear Magnetic Resonance Spectroscopy