Faculty Opinions recommendation of Function of several critical amino acids in human pyruvate dehydrogenase revealed by its structure.

2004 ◽  
Author(s):  
James K Stoops
Keyword(s):  
Amino Acids ◽  
Pyruvate Dehydrogenase

Identification and validation of differentially expressed transcripts in a hepatocyte model of cold-induced glycerol production in rainbow smelt (Osmerus mordax)

2011 ◽  
Vol 301 (4) ◽  
pp. R995-R1010 ◽  
Author(s):  
Jennifer R. Hall ◽  
Kathy A. Clow ◽  
Matthew L. Rise ◽  
William R. Driedzic
Keyword(s):  
Amino Acids ◽  
Low Temperature ◽  
Pyruvate Dehydrogenase ◽  
Cdna Array ◽  
Pyruvate Dehydrogenase Kinase ◽  
Osmerus Mordax ◽  
Type Ii ◽  
Glycerol Production ◽  
Rainbow Smelt ◽  
Transcript Levels

Rainbow smelt ( Osmerus mordax ) avoid freezing by producing antifreeze protein (AFP) and accumulating glycerol. Glyceroneogenesis occurs in liver via a branch in glycolysis and gluconeogenesis and is activated by low temperature. Hepatocytes were isolated from the livers of fish acclimated to 8°C. Cells were incubated at warm (8°C; nonglycerol accumulating) or cold (0.4°C; glycerol accumulating) temperature over a 72-h time course. Reciprocal suppression subtractive hybridization libraries enriched for cold-responsive transcripts were constructed at 72 h. Microarray analyses using a 16K salmonid cDNA array were performed at 24, 48, and 72 h. Expression of type II AFP and 21 carbohydrate, amino acid, or lipid metabolism-related transcripts were validated using quantitative RT-PCR. Type II AFP transcript levels were not directly temperature related. In cold cells, levels of the glucose synthesis transcript were transiently higher. Increased glycerol production was not associated with increased phosphofructokinase or cytosolic glycerol-3-phosphate dehydrogenase transcript levels. Levels of transcripts (phosphoenolpyruvate carboxykinase, mitochondrial malate dehydrogenase, alanine aminotransferase, glutamate dehydrogenase, and aquaglyceroporin 9) associated with mobilization of amino acids to fuel glycerol accumulation were all transiently higher, suggesting a common regulatory mechanism. In cold compared with warm cells, pyruvate dehydrogenase kinase [an inhibitor of pyruvate dehydrogenase (PDH)] transcript levels were 20-fold higher. Potent inhibition of PDH would direct pyruvate and oxaloacetate derived from amino acids to glycerol, as opposed to oxidation via the citric acid cycle. Levels of a transcript potentially encoding glycerol-3-phosphatase, an enzyme not yet characterized in any vertebrate species, were higher following cold incubation. Finally, this study also presents the novel finding of increased glutamine synthetase transcript levels in response to low temperature.

scholarly journals Inactivation of rat adipocyte pyruvate dehydrogenase by palmitate. Protection against this effect by insulin in the presence of glucose

1979 ◽  
Vol 184 (1) ◽  
pp. 59-62 ◽  
Author(s):  
S R Sooranna ◽  
E D Saggerson
Keyword(s):  
Amino Acids ◽  
Fatty Acids ◽  
Dehydrogenase Activity ◽  
Pyruvate Dehydrogenase ◽  
Protective Action ◽  
Active Form ◽  
Rat Plasma ◽  
Epididymal Fat ◽  
Fat Pads

1. Adipocytes from rat epididymal fat-pads were incubated for 30 min with 5 mM-glucose and concentrations of lactate, pyruvate and amino acids typical of those found in rat plasma. 2. PDHa (active form of pyruvate dehydrogenase) activity was significantly increased after incubation of the cells with insulin (200 micro-i.u./ml), and decreased by incubation with palmitate (0.5–2 mM). 3. In the presence of insulin, palmitate did not decrease PDHa activity. 4. Dichloroacetate (1 mM) increased PDHa activity in the absence of palmitate to the same extent as did insulin. In the presence of dichloroacetate but the absence of insulin, palmitate decreased PDHa activity. In the presence of dichloroacetate and insulin, palmitate again did not decrease PDHa activity. 5. It is concluded that, in the presence of glucose, insulin has a strong protective action against inactivation of adipocyte PDHa by fatty acids.

scholarly journals Utilization of l-alanine and l-glutamine by lactating mammary gland of the rat. A role for l-alanine as a lipogenic precursor

1981 ◽  
Vol 196 (3) ◽  
pp. 757-762 ◽  
Author(s):  
J R Viña ◽  
D H Williamson
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Mammary Gland ◽  
Pyruvate Dehydrogenase ◽  
Blood Concentration ◽  
Mammary Glands ◽  
Cafeteria Diet ◽  
Arterial Blood ◽  
Lactating Mammary Gland

1. Lactation is associated with an increase in the arterial blood concentration of L-alanine and L-glutamate, but a decrease in that of L-glutamine compared with the corresponding values for virgin rats. 2. Virgin rats fed a ‘cafeteria diet’ that induces hyperphagia have increased arterial concentrations of L-alanine, L-glutamate and L-glutamine. During lactation L-alanine and L-glutamate concentrations are even higher. 3. The removal of L-alanine is decreased in hepatocytes from lactating rats fed either a chow or cafeteria diet. 4. Measurements of arteriovenous differences across lactating mammary glands indicate that appreciable amounts of L-glutamine and L-alanine are extracted by the gland. 5. A high proportion of the L-alanine metabolized by isolated acini from fed lactating rats is converted into lipid. 6. Metabolism of L-alanine in acini from starved lactating rats is limited by the activity of pyruvate dehydrogenase. 7. It is concluded that L-alanine and certain other amino acids taken up by the gland in excess of the requirements for protein synthesis can be converted into lipid.

scholarly journals Carbohydrate metabolism during prolonged exercise and recovery: interactions between pyruvate dehydrogenase, fatty acids, and amino acids

2006 ◽  
Vol 100 (6) ◽  
pp. 1822-1830 ◽  
Author(s):  
Marina Mourtzakis ◽  
Bengt Saltin ◽  
Terry Graham ◽  
Henriette Pilegaard
Keyword(s):  
Amino Acids ◽  
Fatty Acid ◽  
Amino Acid ◽  
Pyruvate Dehydrogenase ◽  
Prolonged Exercise ◽  
Carbohydrate Oxidation ◽  
Total Amino Acid ◽  
Acid Uptake ◽  
Flow Measurements ◽  
Early Exercise

During prolonged exercise, carbohydrate oxidation may result from decreased pyruvate production and increased fatty acid supply and ultimately lead to reduced pyruvate dehydrogenase (PDH) activity. Pyruvate also interacts with the amino acids alanine, glutamine, and glutamate, whereby the decline in pyruvate production could affect tricarboxycylic acid cycle flux as well as gluconeogenesis. To enhance our understanding of these interactions, we studied the time course of changes in substrate utilization in six men who cycled at 44 ± 1% peak oxygen consumption (mean ± SE) until exhaustion (exhaustion at 3 h 23 min ± 11 min). Femoral arterial and venous blood, blood flow measurements, and muscle samples were obtained hourly during exercise and recovery (3 h). Carbohydrate oxidation peaked at 30 min of exercise and subsequently decreased for the remainder of the exercise bout ( P < 0.05). PDH activity peaked at 2 h of exercise, whereas pyruvate production peaked at 1 h of exercise and was reduced (∼30%) thereafter, suggesting that pyruvate availability primarily accounted for reduced carbohydrate oxidation. Increased free fatty acid uptake ( P < 0.05) was also associated with decreasing PDH activity ( P < 0.05) and increased PDH kinase 4 mRNA ( P < 0.05) during exercise and recovery. At 1 h of exercise, pyruvate production was greatest and was closely linked to glutamate, which was the predominant amino acid taken up during exercise and recovery. Alanine and glutamine were also associated with pyruvate metabolism, and they comprised ∼68% of total amino-acid release during exercise and recovery. Thus reduced pyruvate production was primarily associated with reduced carbohydrate oxidation, whereas the greatest production of pyruvate was related to glutamate, glutamine, and alanine metabolism in early exercise.

scholarly journals Factors regulating amino acid release from extrasplanchnic tissues in the rat. Interactions of alanine and glutamine

1975 ◽  
Vol 150 (3) ◽  
pp. 379-387 ◽  
Author(s):  
P J Blackshear ◽  
P A Holloway ◽  
K G Alberti
Keyword(s):  
Amino Acids ◽  
Glutamine Synthetase ◽  
Pyruvate Dehydrogenase ◽  
Alanine Aminotransferase ◽  
Branched Chain Amino Acids ◽  
Peripheral Tissues ◽  
Acid Release ◽  
Branched Chain ◽  
Methionine Sulphoximine

1. Factors regulating the release of alanine and glutamine in vivo were investigated in starved rats by removing the liver from the circulation and monitoring blood metabolite changes for 30 min. 2. Alanine and glutamine were the predominant amino acids released into the circulation in this preparation. 3. Dichloroacetate, an activator of pyruvate dehydrogenase, inhibited net alanine release: it also interfered with the metabolism of the branched-chain amino acids valine, leucine and isoleucine. 4. L-Cycloserine, an inhibitor of alanine aminotransferase, decreased alanine accumulation by 80% after functional hepatectomy, whereas methionine sulphoximine, an inhibitor of glutamine synthetase, decreased glutamine accumulation by the same amount. 5. It was concluded that: (a) the alanine aminotransferase and the glutamine synthetase pathways respectively were responsible for 80% of the alanine and glutamine released into the circulation by the extrasplanchnic tissues, and extrahepatic proteolysis could account for a maximum of 20%; (b) alanine formation by the peripheral tissues was dependent on availability of pyruvate and not of glutamate; (c) glutamate availability could influence glutamine formation subject, possibly, to renal control.

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