scholarly journals Changes in hepatic lipogenesis during development of the rat

1967 ◽  
Vol 105 (2) ◽  
pp. 717-722 ◽  
Author(s):  
C B Taylor ◽  
E. Bailey ◽  
W Bartley
Keyword(s):  
Enzyme Activity ◽  
Pyruvate Kinase ◽  
Malic Enzyme ◽  
Female Rats ◽  
Male Rats ◽  
Acetate Incorporation ◽  
Atp Citrate Lyase ◽  
Citrate Lyase ◽  
Malic Enzyme Activity ◽  
Glucose 6 Phosphate Dehydrogenase

1. Changes in the activities of ATP citrate lyase, ‘malic’ enzyme, glucose 6-phosphate dehydrogenase, pyruvate kinase and fructose 1,6-diphosphatase, and in the ability to incorporate [1−14C]acetate into lipid have been measured in the livers of developing rats between late foetal life and maturity. 2. In male rats the activities of those systems directly or indirectly concerned in lipogenesis (acetate incorporation into lipid, ATP citrate lyase and glucose 6-phosphate dehydrogenase) fall after birth and are maintained at a low value until weaning. After weaning these activities rise to a maximum between 30 and 40 days and then decline, reaching adult values at about 60 days. ‘Malic’ enzyme activity follows a similar course, except that none could be detected in the foetal liver. Pyruvate kinase activity is lower in foetal than in adult livers and rises to slightly higher than the adult value in the post-weaning period. Fructose 1,6-diphosphatase activity rises from a very low foetal value to reach a maximum at about 10 days but falls rapidly after weaning to reach adult values at about 30 days. 3. Weaning rats on to a high-fat diet caused the low activities of acetate incorporation, ATP citrate lyase, glucose 6-phosphate dehydrogenase and pyruvate kinase, characteristic of the suckling period, to persist. ‘Malic’ enzyme and fructose 1,6-diphosphatase activities were not altered appreciably. 4. No differences could be detected in hepatic enzyme activities between males and females up to 35 days, but after this time female rats gave higher values for acetate incorporation, glucose 6-phosphate dehydrogenase activity and ‘malic’ enzyme activity. 5. The results are discussed in relation to changes in alimentation and hormonal influences.

scholarly journals Factors involved in changes in hepatic lipogenesis during development of the rat

1970 ◽  
Vol 118 (1) ◽  
pp. 155-162 ◽  
Author(s):  
Elizabeth A. Lockwood ◽  
E. Bailey ◽  
C. B. Taylor
Keyword(s):  
Enzyme Activities ◽  
Malic Enzyme ◽  
Hormonal Control ◽  
Male Rats ◽  
Acetyl Coa Carboxylase ◽  
Hepatic Enzymes ◽  
Atp Citrate Lyase ◽  
Acetyl Coa ◽  
Citrate Lyase ◽  
Glucose 6 Phosphate Dehydrogenase

1. Changes in the activities of acetyl-CoA carboxylase (EC 6.4.1.2), phosphofructokinase (EC 2.7.1.11), aldolase (EC 4.1.2.13), extramitochondrial aconitate hydratase (EC 4.2.1.3) and NADP-dependent isocitrate dehydrogenase (EC 1.1.1.42) have been measured in the livers of developing rats from late foetal life to maturity. 2. The effect of altering the weaning time on some enzymes associated with lipogenesis has been studied. Weaning rats at 15 days of age instead of 21 days results in an immediate increase in the activity of `malic' enzyme (EC 1.1.1.40) whereas the activities of glucose 6-phosphate dehydrogenase (EC 1.1.1.49) and ATP citrate lyase (EC 4.1.3.8) did not increase until 4–5 days and acetyl-CoA carboxylase 2–3 days after early weaning. Weaning rats on to an artificial-milk diet led to complete repression of the rise in activity of hepatic enzymes associated with lipogenesis normally found on weaning, except for `malic' enzyme, which increased in activity after 20 days of age. 3. The effect of intraperitoneal injections of glucagon, cortisol, growth hormone and thyroxine on the same hepatic enzymes has been investigated. Only thyroxine had any effect on enzyme activities and caused a 20-fold increase in `malic' enzyme activity and a twofold increase in ATP citrate lyase activity. 4. The activities of hepatic glucose 6-phosphate dehydrogenase and `malic' enzyme are higher in adult female than in adult male rats and it has been shown that this sex difference in enzyme activities is due to both male and female sex hormones. 5. Hepatic malate, citrate, pyruvate, glucose 6-phosphate and phosphoenolpyruvate concentrations have been measured throughout development. 6. The results are discussed in relation to the dietary and hormonal control of hepatic enzyme activities during development.

Time-course of enzyme adaptation. I. Effects of substituting dietary glucose and fructose at constant concentrations of dietary protein

1968 ◽  
Vol 46 (12) ◽  
pp. 1459-1470 ◽  
Author(s):  
B. Szepesi ◽  
R. A. Freedland
Keyword(s):  
Enzyme Activity ◽  
Pyruvate Kinase ◽  
Dietary Protein ◽  
Malic Enzyme ◽  
Dietary Change ◽  
Phosphogluconate Dehydrogenase ◽  
Dietary Fructose ◽  
Liver And Kidney ◽  
Malic Enzyme Activity ◽  
Glucose 6 Phosphate Dehydrogenase

The effect of dietary fructose on liver, kidney, and adrenal enzymes was studied in male Sprague–Dawley rats. Dietary fructose increased relative liver and kidney sizes, liver glycogen, and liver protein. The percentage increases in relative liver and kidney sizes were independent of dietary protein, but relative liver sizes were smaller in the absence of protein.The activities of all the liver enzymes studied, except glucokinase, were increased by a 65% fructose diet containing 25% casein. The rates of increases differed between enzymes; the activities of L-α-glycerophosphate dehydrogenase and phosphoenolpyruvate carboxykinase (PEP-carboxykinase) reached almost maximum in 1 day, glucose 6-phosphatase, 6-phosphogluconate dehydrogenase, and pyruvate kinase activities reached maximum in about 2 days, and glucose 6-phosphate dehydrogenase, malic enzyme, dihydroxyacetone kinase, phosphofructose kinase, and phosphohexose isomerase required at least 3 days to reach maximum activity after the dietary change. The increases in the activities of liver fructose 1,6-diphosphatase, glucose 6-phosphate dehydrogenase, pyruvate kinase, and phosphohexose isomerase did not occur in the absence of dietary protein. The activities of liver phosphofructokinase and malic enzyme were increased equally well whether the fructose diet contained protein or not, while the increases in the activities of other enzymes were less in the absence of dietary protein.The half-life of liver malic enzyme was estimated as 3 days in the glucose to fructose dietary change and 1 day in the fructose to glucose dietary change. Since malic enzyme activity was increased by fructose feeding about threefold, the data suggest that under the conditions of the experiment fructose increased malic enzyme activity by decreasing the rate of breakdown of the enzyme.In general, kidney enzymes were affected by fructose to a lesser extent than the corresponding enzymes in liver. This was particularly significant in the case of kidney glucose 6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, and malic enzyme, the activities of which were only slightly increased in kidney. The activities of these three enzymes in the adrenal glands were not increased by fructose feeding.

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.

scholarly journals EFFECTS OF HORMONES ON HEPATIC GLUCOSE 6-PHOSPHATE DEHYDROGENASE OF RAT

1967 ◽  
Vol 15 (9) ◽  
pp. 530-534 ◽  
Author(s):  
SAMUEL H. HORI ◽  
SEI-ICHI MATSUI
Keyword(s):  
Enzyme Activity ◽  
Sex Difference ◽  
Total Activity ◽  
Estradiol Benzoate ◽  
Isozyme Pattern ◽  
Female Rats ◽  
Male Rats ◽  
Total Enzyme Activity ◽  
Male And Female Rats ◽  
Glucose 6 Phosphate Dehydrogenase

The effects of hormones on the total activity and the isozyme pattern of glucose 6-phosphate dehydrogenase of livers of normal, castrated and adrenalectomized rats were studied. Sex difference in total enzyme activity and in the activity of one of the seven isozymes separated electrophoretically (band D enzyme) has been confirmed. Orchidectomy did not affect appreciably the enzyme activity; ovariectomy of young rats reduced the enzyme activity and abolished the sex difference. Adrenalectomy slightly reduced the enzyme activity in male and female rats, but did not eliminate the sex difference in isozyme pattern. Injection of dehydroepiandrosterone into normal and castrated female rats lowered the enzyme activity, whereas administration of estradiol benzoate to normal and castrated male rats strikingly increased the enzyme activity. In estradiol-treated males the isozyme pattern become female type. The effect of estradiol was inhibited by puromycin. Estradiol stimulated but dehydroepiandrosterone had little effect on hepatic 6-phosphogluconate dehydrogenase activity.

Morphological and biochemical analyses of changes in rat hepatocytes related to wine and ethanol consumption

1984 ◽  
Vol 42 ◽  
pp. 232-233
Author(s):  
S.M. Geyer ◽  
C.L. Mendenhall ◽  
J.T. Hung ◽  
E.L. Cardell ◽  
R.L. Drake ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Endoplasmic Reticulum ◽  
Enzyme Activity ◽  
Malic Enzyme ◽  
Smooth Endoplasmic Reticulum ◽  
Rat Hepatocytes ◽  
Mature Male ◽  
Treatment Groups ◽  
Malic Enzyme Activity ◽  
Biochemical Analyses

Thirty-three mature male Holtzman rats were randomly placed in 3 treatment groups: Controls (C); Ethanolics (E); and Wine drinkers (W). The animals were fed synthetic diets (Lieber type) with ethanol or wine substituted isocalorically for carbohydrates in the diet of E and W groups, respectively. W received a volume of wine which provided the same gram quantity of alcohol consumed by E. The animals were sacrificed by decapitation after 6 weeks and the livers processed for quantitative triglycerides (T3), proteins, malic enzyme activity (MEA), light microscopy (LM) and electron microscopy (EM). Morphometric analysis of randomly selected LM and EM micrographs was performed to determine organellar changes in centrilobular (CV) and periportal (PV) regions of the liver. This analysis (Table 1) showed that hepatocytes from E were larger than those in C and W groups. Smooth endoplasmic reticulum decreased in E and increased in W compared to C values.

‘Malic Enzyme’ Activity in Blowfly Muscle

Nature ◽  
1956 ◽  
Vol 177 (4514) ◽  
pp. 842-843 ◽  
Author(s):  
S. E. LEWIS ◽  
G. M. PRICE
Keyword(s):  
Enzyme Activity ◽  
Malic Enzyme ◽  
Malic Enzyme Activity
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