scholarly journals Citrate-cleavage enzyme, ‘malic’ enzyme and certain dehydrogenases in embryonic and growing chicks

1968 ◽  
Vol 108 (4) ◽  
pp. 663-666 ◽  
Author(s):  
Alan G. Goodridge
Keyword(s):  
Adipose Tissue ◽  
Malic Enzyme ◽  
Fold Increase ◽  
Hexose Monophosphate ◽  
Hexose Monophosphate Shunt ◽  
Glycerophosphate Dehydrogenase ◽  
Cleavage Enzyme ◽  
Malic Enzyme Activity ◽  
Relationship Of

The activities of several enzymes possibly implicated in lipogenesis were measured in the soluble fraction of homogenates of liver and adipose tissue of embryonic and growing chicks. The activities of adipose-tissue enzymes showed little or no change. The activities of hepatic hexose monophosphate-shunt dehydrogenases, malate dehydrogenase, 3-phosphoglyceraldehyde dehydrogenase and NAD-linked α-glycerophosphate dehydrogenase also showed little or no change. Isocitrate dehydrogenase activity in liver rose to a peak on the day of hatching and fell to half the peak value during the next 12 days, where it remained to 26 days after hatching. The activities of ‘malic’ enzyme and citrate-cleavage enzyme showed very low stable values in embryonic liver and remarkable rises during the early part of the post-hatching period. An 85-fold increase in the activity of ‘malic’ enzyme activity was completed in 7 days and a 15-fold increase in that of citrate-cleavage enzyme in 5 days. The activities then attained were maintained up to 26 days after hatching. 2. The increases in the activities of hepatic citrate-cleavage enzyme and ‘malic’ enzyme occurred simultaneously with a marked increase in lipogenesis, suggesting a relationship of these enzymes to lipogenesis in chick liver. By contrast, activity of the hexose monophosphate-shunt dehydrogenases does not appear to be thus associated.

scholarly journals The effect of starvation and starvation followed by feeding on enzyme activity and the metabolism of [U−14C]glucose in liver from growing chicks

1968 ◽  
Vol 108 (4) ◽  
pp. 667-673 ◽  
Author(s):  
Alan G. Goodridge
Keyword(s):  
Fatty Acids ◽  
Enzyme Activity ◽  
Fatty Acid ◽  
Isocitrate Dehydrogenase ◽  
Malic Enzyme ◽  
Acid Synthesis ◽  
Minor Role ◽  
Hexose Monophosphate ◽  
Hexose Monophosphate Shunt ◽  
Cleavage Enzyme

1. The conversion of [U−14C]glucose into carbon dioxide, cholesterol and fatty acids in liver slices and the activities of ‘malic’ enzyme, citrate-cleavage enzyme, NADP-linked isocitrate dehydrogenase and hexose monophosphate-shunt dehydrogenases in the soluble fraction of homogenates of liver were measured in chicks that were starved or starved then fed. 2. In newly hatched chicks the incorporation of [U−14C]glucose and the activity of ‘malic’ enzyme did not increase unless the birds were fed. The response to feeding of [U−14C]glucose incorporation into fatty acids increased as the starved chicks grew older. 3. Citrate-cleavage enzyme activity increased slowly even when the newly hatched chicks were unfed. On feeding, citrate-cleavage enzyme activity increased at a much faster rate. 4. In normally fed 20-day-old chicks starvation decreased the incorporation of [U−14C]glucose into all three end products and depressed the activities of ‘malic’ enzyme and citrate-cleavage enzyme. Re-feeding increased all of these processes to normal or higher-than-normal levels. 5. In both newly hatched and 20-day-old chicks starvation increased the activity of isocitrate dehydrogenase and feeding or re-feeding decreased it. 6. Very little change in hexose monophosphate-shunt dehydrogenase activity was observed during the dietary manipulations. 7. The results indicate that increased substrate delivery to the liver is the principal stimulus to the increased rate of glucose metabolism observed in newly hatched chicks. The results also suggest that changes in the activities of ‘malic’ enzyme and citrate-cleavage enzyme are secondary to an increased flow of metabolites through the glucose-to-fatty acid pathway and that the dehydrogenases of the hexose monophosphate shunt play a minor role in NADPH production for fatty acid synthesis.

scholarly journals Identification and Characterization ofMAE1, the Saccharomyces cerevisiae Structural Gene Encoding Mitochondrial Malic Enzyme

1998 ◽  
Vol 180 (11) ◽  
pp. 2875-2882 ◽  
Author(s):  
Eckhard Boles ◽  
Patricia de Jong-Gubbels ◽  
Jack T. Pronk
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Enzyme Activity ◽  
Pyruvate Kinase ◽  
Malic Enzyme ◽  
Fold Increase ◽  
Growth Conditions ◽  
Anaerobic Growth ◽  
Oxidative Decarboxylation ◽  
Mrna Levels ◽  
Malic Enzyme Activity

ABSTRACT Pyruvate, a precursor for several amino acids, can be synthesized from phosphoenolpyruvate by pyruvate kinase. Nevertheless, pyk1 pyk2 mutants of Saccharomyces cerevisiae devoid of pyruvate kinase activity grew normally on ethanol in defined media, indicating the presence of an alternative route for pyruvate synthesis. A candidate for this role is malic enzyme, which catalyzes the oxidative decarboxylation of malate to pyruvate. Disruption of open reading frame YKL029c, which is homologous to malic enzyme genes from other organisms, abolished malic enzyme activity in extracts of glucose-grown cells. Conversely, overexpression ofYKL029c/MAE1 from the MET25 promoter resulted in an up to 33-fold increase of malic enzyme activity. Growth studies with mutants demonstrated that presence of either Pyk1p or Mae1p is required for growth on ethanol. Mutants lacking both enzymes could be rescued by addition of alanine or pyruvate to ethanol cultures. Disruption of MAE1 alone did not result in a clear phenotype. Regulation of MAE1 was studied by determining enzyme activities and MAE1 mRNA levels in wild-type cultures and by measuring β-galactosidase activities in a strain carrying a MAE1::lacZ fusion. Both in shake flask cultures and in carbon-limited chemostat cultures,MAE1 was constitutively expressed. A three- to fourfold induction was observed during anaerobic growth on glucose. Subcellular fractionation experiments indicated that malic enzyme in S. cerevisiae is a mitochondrial enzyme. Its regulation and localization suggest a role in the provision of intramitochondrial NADPH or pyruvate under anaerobic growth conditions. However, since null mutants could still grow anaerobically, this function is apparently not essential.

Metabolic alterations after dehydroepiandrosterone treatment in Zucker rats

1984 ◽  
Vol 246 (2) ◽  
pp. E123-E128 ◽  
Author(s):  
A. Shepherd ◽  
M. P. Cleary
Keyword(s):  
Enzyme Activity ◽  
Adipose Tissue ◽  
Fatty Acid ◽  
Malic Enzyme ◽  
Fatty Acid Synthetase ◽  
Metabolic Effects ◽  
Zucker Rats ◽  
Obese Rats ◽  
Malic Enzyme Activity ◽  
Dhea Treatment

Dehydroepiandrosterone (DHEA) is a known noncompetitive inhibitor of glucose-6-phosphate dehydrogenase (G6PD). In the present investigation, the effects of chronic DHEA treatment on G6PD and several other enzymes involved in lipid metabolism were examined in lean and obese Zucker rats. Significant decreases in body weight were found in DHEA-treated rats in comparison with nontreated rats. In lean rats, DHEA treatment did not decrease either liver or adipose tissue G6PD and fatty acid synthetase activity, but malic enzyme activity was increased. In obese rats, decreased liver and adipose tissue G6PD and fatty acid synthetase activities were found. Malic enzyme activity in liver of obese DHEA rats was increased but not in adipose tissue. Adipose tissue lipoprotein lipase activity was decreased in both lean and obese DHEA rats. Serum insulin in obese DHEA rats was also decreased compared with control obese rats. These results indicate that the inhibition of G6PD may not be the mechanism of action of the antiobesity effect of DHEA. However, the metabolic effects of DHEA seen in obese rats may contribute to its antiobesity action.

scholarly journals Activity of selected gluconeogenic and lipogenic enzymes in bovine rumen mucosa, liver and adipose tissue

1969 ◽  
Vol 114 (1) ◽  
pp. 83-88 ◽  
Author(s):  
Jerry W. Young ◽  
Sylvia L. Thorp ◽  
Helen Z. De Lumen
Keyword(s):  
Enzyme Activity ◽  
Adipose Tissue ◽  
Dehydrogenase Activity ◽  
Malic Enzyme ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Lipogenic Enzymes ◽  
Adipose Tissues ◽  
Cleavage Enzyme ◽  
Glucose 6 Phosphate Dehydrogenase ◽  
Enzyme Patterns

The activities of phosphoenolpyruvate carboxykinase, ‘malic enzyme’, citrate-cleavage enzyme and glucose 6-phosphate dehydrogenase were assayed in homogenates of rumen mucosa, liver and adipose tissue of cattle. Rumen mucosa cytoplasm contained activities of ‘malic enzyme’ approximately sevenfold those of phosphoenolpyruvate carboxykinase, suggesting that the conversion of propionate into lactate by rumen mucosa involves ‘malic enzyme’. Neither starvation for 8 days nor feeding with a concentrate diet for at least 3 months before slaughter produced enzyme patterns in the tissues different from those in cattle given only hay, except that the all-concentrate diet caused increased activities of glucose 6-phosphate dehydrogenase and ‘malic enzyme’ in adipose tissues. Rumen mucosa, liver and adipose tissue contained phosphoenolpyruvate carboxykinase activity. ‘Malic enzyme’ was absent in liver. Citrate-cleavage enzyme activity was present in liver and adipose tissue but was quite low in rumen mucosa. Liver contained much less glucose 6-phosphate dehydrogenase activity than rumen mucosa or adipose tissue.

scholarly journals Reassessment of the Transhydrogenase/Malate Shunt Pathway in Clostridium thermocellum ATCC 27405 through Kinetic Characterization of Malic Enzyme and Malate Dehydrogenase

2015 ◽  
Vol 81 (7) ◽  
pp. 2423-2432 ◽  
Author(s):  
M. Taillefer ◽  
T. Rydzak ◽  
D. B. Levin ◽  
I. J. Oresnik ◽  
R. Sparling
Keyword(s):  
Malate Dehydrogenase ◽  
Malic Enzyme ◽  
Clostridium Thermocellum ◽  
Consolidated Bioprocessing ◽  
Catalytic Efficiency ◽  
Fold Increase ◽  
Cellulosic Biomass ◽  
Content Type ◽  
Malic Enzyme Activity

ABSTRACTClostridium thermocellumproduces ethanol as one of its major end products from direct fermentation of cellulosic biomass. Therefore, it is viewed as an attractive model for the production of biofuels via consolidated bioprocessing. However, a better understanding of the metabolic pathways, along with their putative regulation, could lead to improved strategies for increasing the production of ethanol. In the absence of an annotated pyruvate kinase in the genome, alternate means of generating pyruvate have been sought. Previous proteomic and transcriptomic work detected high levels of a malate dehydrogenase and malic enzyme, which may be used as part of a malate shunt for the generation of pyruvate from phosphoenolpyruvate. The purification and characterization of the malate dehydrogenase and malic enzyme are described in order to elucidate their putative roles in malate shunt and their potential role inC. thermocellummetabolism. The malate dehydrogenase catalyzed the reduction of oxaloacetate to malate utilizing NADH or NADPH with akcatof 45.8 s−1or 14.9 s−1, respectively, resulting in a 12-fold increase in catalytic efficiency when using NADH over NADPH. The malic enzyme displayed reversible malate decarboxylation activity with akcatof 520.8 s−1. The malic enzyme used NADP+as a cofactor along with NH4+and Mn2+as activators. Pyrophosphate was found to be a potent inhibitor of malic enzyme activity, with aKiof 0.036 mM. We propose a putative regulatory mechanism of the malate shunt by pyrophosphate and NH4+based on the characterization of the malate dehydrogenase and malic enzyme.

Concomitant Repression by Gluten of HMP Shunt Dehydrogenases, Citrate Cleavage Enzyme and Malic Enzyme in Rat Liver and Adipose Tissue

1976 ◽  
Vol 106 (3) ◽  
pp. 335-341 ◽  
Author(s):  
Gaetano Livrea ◽  
Giovanni Carrozza ◽  
Luigi Manasseri ◽  
Ugo Muraca
Keyword(s):  
Adipose Tissue ◽  
Rat Liver ◽  
Malic Enzyme ◽  
Cleavage Enzyme
Sign in / Sign up

Export Citation Format

Share Document