scholarly journals Phosphopyruvate carboxylase induction by l-tryptophan. Effects on synthesis and degradation of the enzyme

1973 ◽  
Vol 136 (2) ◽  
pp. 259-264 ◽  
Author(s):  
F. J. Ballard ◽  
M. F. Hopgood
Keyword(s):  
Enzyme Activity ◽  
Specific Antibody ◽  
Actinomycin D ◽  
Relative Rate ◽  
Enzyme Synthesis ◽  
Enzyme Protein ◽  
Carboxylase Activity ◽  
Twofold Increase ◽  
Synthesis And Degradation

1. The administration of l-tryptophan to fed rats produces a twofold increase in hepatic phosphopyruvate carboxylase activity that represents a comparable increase in enzyme protein. With specific antibody against the enzyme we have shown that the increase in phosphopyruvate carboxylase is partially mediated via an actinomycin D-sensitive increase in enzyme synthesis. 2. In starved animals tryptophan increases the enzyme activity without any change in the relative rate of phosphopyruvate carboxylase synthesis. In this condition degradation of the enzyme is retarded by tryptophan by a mechanism that is not prevented by cycloheximide.

scholarly journals TEMPORAL ORDER IN MAMMALIAN CELLS

1969 ◽  
Vol 43 (2) ◽  
pp. 207-219 ◽  
Author(s):  
Robert R. Klevecz
Keyword(s):  
Enzyme Activity ◽  
Mammalian Cells ◽  
Temporal Order ◽  
Actinomycin D ◽  
Chinese Hamster ◽  
Enzyme Synthesis ◽  
S Phase ◽  
Selection System ◽  
Enzyme Protein ◽  
Chinese Hamster Cells

Chinese hamster cells were synchronized by the Colcemid-selection system. In cells with a division cycle time of 11.5–12 hr, the activity of the enzyme lactate dehydrogenase (LDH) underwent marked oscillations with a 3.5-hr period. Precipitation of labeled LDH enzyme with specific antibody indicated that the enzyme activity changes were the result of intermittent enzyme synthesis and relatively constant degradation. Inhibition of normal DNA replication with 4 mM of thymidine, while reducing the amount of new enzyme synthesized, did not prevent oscillations from occurring. Similarly, actinomycin D (AcD) added at the time of synchronization allowed some new enzyme synthesis to proceed in an oscillatory manner. LDH synthesis went on at nearly normal rates when AcD was added in the middle of S phase. However, addition of cycloheximide to cultures at any time in the cycle caused an immediate drop in levels of activity and in enzyme protein. The half-life of LDH, calculated either from loss of enzyme activity or precipitable radioactivity in cycloheximide-treated cultures, was between 2 and 2.5 hr.

scholarly journals Nutritional and hormonal regulation of malic enzyme synthesis in rat mammary gland

1986 ◽  
Vol 236 (2) ◽  
pp. 441-445 ◽  
Author(s):  
M F Lobato ◽  
M Ros ◽  
F J Moreno ◽  
J P García-Ruíz
Keyword(s):  
Enzyme Activity ◽  
Mammary Gland ◽  
Malic Enzyme ◽  
Hormonal Regulation ◽  
Relative Rate ◽  
Enzyme Synthesis ◽  
Soluble Proteins ◽  
Control Value ◽  
Rat Mammary Gland ◽  
Malic Enzyme Activity

Cytosolic malic enzyme was purified from rat mammary gland by L-malate affinity chromatography. The pure enzyme obtained was used to produce a specific antiserum in a rabbit. Relative synthesis of malic enzyme in the mammary gland of mid-lactating rats was 0.097%, measured by labelling the enzyme in isolated acini. When food was removed, malic enzyme synthesis decreased to 35% and 20% of the control value at 4 and 6 h respectively. Incorporation of [3H]leucine into soluble proteins was constant during the first 6 h of starvation. When lactating rats (maintained with their pups) were starved for 24 h and then re-fed, the relative rate of enzyme synthesis increased 2.5-, 4-, and 4.5-fold at 3 h, 6 h and 18 h respectively after initiation of re-feeding. The relative rate of malic enzyme synthesis was about 50% of normal at 15 h after weaning, whereas the rate of synthesis of soluble proteins did not change. Administration of bromocriptine or adrenalectomy of lactating rats decreased the relative rate of synthesis of malic enzyme by 40% or 30% respectively; these effects were counteracted by hormone supplementation. Hormone therapy also caused an increase in the rate of incorporation of [3H]leucine into soluble proteins and in malic enzyme activity.

scholarly journals Glucose-dependent induction of acetyl-CoA carboxylase in rat hepatocyte cultures

1984 ◽  
Vol 221 (2) ◽  
pp. 343-350 ◽  
Author(s):  
S Giffhorn ◽  
N R Katz
Keyword(s):  
Enzyme Activity ◽  
Enzyme Level ◽  
Enzyme Synthesis ◽  
Acetyl Coa Carboxylase ◽  
Enzyme Protein ◽  
Atp Citrate Lyase ◽  
Acetyl Coa ◽  
Adult Rats ◽  
Hepatocyte Cultures

The carbohydrate-dependent long-term regulation of acetyl-CoA carboxylase was studied in primary hepatocyte cultures from adult rats. (1) The enzyme activity was increased 2-fold either by elevation of the glucose concentration to 20mM or by enhancement of the insulin concentration to 0.1 microM. Simultaneous increases in glucose and insulin resulted in a 5-fold increase in the enzyme activity. (2) As shown by immunochemical titration, the enhancement of the enzyme activity was due to an increase in the enzyme protein. (3) Incorporation of [35S]methionine and immunoprecipitation of the enzyme revealed that the increase in enzyme protein was due to an increased rate of enzyme synthesis. The rate of enzyme degradation remained essentially unchanged. (4) The glucose- and insulin-dependent induction of acetyl-CoA carboxylase was prevented by the addition of alpha-amanitin (10 microM) or cordycepin (10 microM), indicating a transcriptional regulation of the enzyme level. (5) The parallel induction of acetyl-CoA carboxylase and of ATP citrate lyase indicates a co-ordinate long-term regulation of lipogenic enzymes.

scholarly journals Turnover of succinyl-CoA:3-oxoacid CoA-transferase in glioma and neuroblastoma cells. Specific influence of acetoacetate in neuroblastoma cells

1984 ◽  
Vol 224 (1) ◽  
pp. 67-74 ◽  
Author(s):  
P M Haney ◽  
L Bolinger ◽  
C Raefsky ◽  
M S Patel
Keyword(s):  
Cell Lines ◽  
Specific Activity ◽  
Relative Rate ◽  
Neuroblastoma Cells ◽  
Glioma Cells ◽  
Enzyme Synthesis ◽  
Exponential Growth Phase ◽  
Enzyme Protein ◽  
Coa Transferase ◽  
Degradation Rates

The specific activity of succinyl-CoA:3-oxo-acid CoA-transferase (3-oxoacid CoA-transferase, EC 2.8.3.5) increases significantly during growth in culture in both mouse neuroblastoma N2a and rat glioma C6 cells. To investigate the mechanism(s) responsible for this, antibody specific for rat brain 3-oxoacid CoA-transferase was raised in rabbits. Immunotitrations of 3-oxoacid CoA-transferase from neuroblastoma and glioma cells on days 3 and 7 of growth after subculture showed that the ratio of 3-oxoacid CoA-transferase activity to immunoprecipitable enzyme protein remained constant, indicating that differences in specific activity of the enzyme at these times in both cell types reflect differences in concentration of enzyme protein. In glioma cells, the relative rate of 3-oxoacid CoA-transferase synthesis was about 0.04-0.05% throughout 9 days in culture. In contrast, the relative rate of synthesis of 3-oxo-acid CoA-transferase in neuroblastoma cells was about 0.07-0.08% on days 3, 5 and 7 after subculture, but fell to 0.052% on day 9. The degradation rates of total cellular protein (t1/2 = 28 h) and 3-oxoacid CoA-transferase (t1/2 = 46-50 h) were similar in both cell lines. The rise in specific activity of the enzyme in both cell lines from days 3 to 7 without a significant increase in the relative rate of synthesis reflects a slow approach to steady-state conditions for the enzyme secondary to its slow degradation. Differences in 3-oxoacid CoA-transferase specific activity between the two cell lines are apparently due to a difference of about 60% in relative rates of enzyme synthesis. The presence of 0.5 mM-acetoacetate in the medium significantly increased the specific activity of 3-oxoacid CoA-transferase in neuroblastoma cells during the early exponential growth phase. This treatment increased the relative rate of synthesis of 3-oxoacid CoA-transferase by 23% (P less than 0.025) in these cells on day 3, suggesting that substrate-mediated induction of enzyme synthesis is a mechanism of regulation of 3-oxoacid CoA-transferase.

THE EFFECT OF OESTRADIOL-17β ON ENZYMES CONCERNED WITH METABOLISM OF CARBOHYDRATE IN HUMAN ENDOMETRIUM IN VITRO

1969 ◽  
Vol 44 (1) ◽  
pp. 63-NP ◽  
Author(s):  
E. W. WILSON
Keyword(s):  
Enzyme Activity ◽  
Actinomycin D ◽  
Human Endometrium ◽  
Enzyme Protein ◽  
Quantitative Histochemistry ◽  
Qualitative And Quantitative ◽  
Hormonal Effect ◽  
Lactate Dehydrogenases ◽  
Regenerative Phase

SUMMARY Human endometrium in the regenerative phase was maintained for 5 hr. in vitro with oestradiol-17β alone or together with actinomycin D. Qualitative and quantitative histochemistry of the tissue showed that the activities of glucose-6-phosphate, 6-phosphogluconate, and lactate dehydrogenases were increased by oestradiol, and that actinomycin suppressed the hormonal effect. The activities of succinate and iso-citrate dehydrogenases were unaffected by oestradiol. An attempt is made to correlate the metabolic roles of the enzymes affected by oestradiol. The suppression, by actinomycin, of the oestradiol effect suggests that the increased enzyme activity is due to the formation of new enzyme protein.

scholarly journals Factors affecting the premature induction of phosphopyruvate carboxylase in neonatal rat liver

1968 ◽  
Vol 108 (2) ◽  
pp. 325-331 ◽  
Author(s):  
D. Yeung ◽  
I. T. Oliver
Keyword(s):  
Rat Liver ◽  
Actinomycin D ◽  
Blood Glucose Concentration ◽  
Enzyme Synthesis ◽  
Neonatal Rat ◽  
Carboxylase Activity ◽  
Factors Affecting ◽  
Glucose Injection ◽  
Enzyme Development ◽  
Amino Acid Analogues

1. Phosphopyruvate carboxylase activity rapidly appears in the liver of prematurely delivered rats and development of activity is prevented by injection of actinomycin D just before delivery. 2. The activity is considerably decreased by puromycin and amino acid analogues and thus appears to be due to enzyme synthesis. 3. Newborn or premature animals show a transient intense phase of hypoglycaemia after delivery. 4. When the hypoglycaemic phase is prevented by glucose injection little phosphopyruvate carboxylase activity appears in the liver, but galactose, mannose and fructose, which have no effect on the blood glucose concentration, also repress enzyme development. 5. Lactate, pyruvate and glycerol injections repress the premature development of phosphopyruvate carboxylase. 6. Injections of glucagon, adrenalin and noradrenalin into the rat foetus in utero result in development of phosphopyruvate carboxylase activity. 7. These findings are discussed in relation to the mechanism of initiation of enzyme synthesis in neonatal rat liver.

scholarly journals Effect of streptozotocin-induced diabetes mellitus on the turnover of rat liver pyruvate carboxylase and pyruvate dehydrogenase

1980 ◽  
Vol 188 (3) ◽  
pp. 601-608 ◽  
Author(s):  
M B Weinberg ◽  
M F Utter
Keyword(s):  
Pyruvate Dehydrogenase ◽  
Pyruvate Carboxylase ◽  
Pyruvate Dehydrogenase Complex ◽  
Mitochondrial Protein ◽  
Diabetic Rats ◽  
Pulse Labelling ◽  
Enzyme Protein ◽  
Carboxylase Activity ◽  
Streptozotocin Induced Diabetes ◽  
Synthesis And Degradation

Immunochemical techniques were used to study the effect of streptozotocin-induced diabetes on the amounts of pyruvate carboxylase and pyruvate dehydrogenase and on their rates of synthesis and degradation. Livers from diabetic rats had twice the pyruvate carboxylase activity of livers from normal rats when expressed in terms of DNA or body weight. The changes in catalytic activity closely paralleled changes in immunoprecipitable enzyme protein. Relative rates of synthesis determined by pulse-labelling studies showed that the ratio of synthesis of pyruvate carboxylase to that of average mitochondrial protein was increased 2.0-2.5 times in diabetic animals over that of control animals. Other radioisotopic studies indicated that the rate of degradation of this enzyme was not altered significantly in diabetic rats, suggesting that the increase in this enzyme was due to an increased rate of synthesis. Similar experiments with pyruvate dehydrogenase, the first component of the pyruvate dehydrogenase complex, showed that livers from diabetic rats had approximately the same amount of immunoprecipitable enzyme protein as the control animals, but a larger proportion of the enzyme was in its inactive state. The rates of synthesis and degradation of pyruvate dehydrogenase were not affected significantly by diabetes.

Induction of tyrosinase by L-methionine in Streptomyces antibioticus

1988 ◽  
Vol 34 (12) ◽  
pp. 1297-1303 ◽  
Author(s):  
Edward Katz ◽  
Aline Betancourt
Keyword(s):  
Enzyme Activity ◽  
Actinomycin D ◽  
Enzyme Synthesis ◽  
Streptomyces Antibioticus ◽  
Activity Inhibition

Investigations were carried out to establish conditions favorable for the formation of tyrosinase, an inducible metalloenzyme synthesized by Streptomyces antibioticus. It was determined that the size of the inoculum and age of the culture as well as the temperature of incubation were important factors for enzyme synthesis. Induction of tyrosinase by S. antibioticus appears to be specific for L-methionine with maximal enzyme synthesis observed at 0.1 mM. Addition of CuSO4 and D-glucose at the time of induction also are important for increased enzyme activity. Inhibition of tyrosinase synthesis was observed with actinomycin D, rifampicin, and chloramphenicol suggesting that both transcriptional and translational events are required for tyrosinase induction.

scholarly journals Activities of α-galactosidase and polygalacturonase during hydration of Dalbergia nigra ((Vell.) Fr All. ex Benth.) seeds at different temperatures

2013 ◽  
Vol 35 (1) ◽  
pp. 92-98 ◽  
Author(s):  
Glauciana da Mata Ataíde ◽  
Eduardo Euclydes de Lima e Borges ◽  
José Francisco de Carvalho Gonçalves ◽  
Valéria Monteze Guimarães ◽  
Elisa Monteze Bicalho ◽  
...  
Keyword(s):  
Enzyme Activity ◽  
Relative Humidity ◽  
Water Uptake ◽  
Enzyme Synthesis ◽  
High Relative Humidity ◽  
Different Temperatures ◽  
Glucose Synthesis ◽  
Dalbergia Nigra ◽  
Different Origins ◽  
Synthesis And Degradation

Germination is a process that begins with seed water uptake, stimulating enzyme synthesis or activating enzymes already present. The objective of this study was to evaluate variations in monosaccharide reserves and the activities of the α-galactosidase and polygalacturonase enzymes during the hydration of two lots of Dalbergia nigra (Bahia Rosewood) seeds. Seeds from different origins constituted the two lots I and II, classified as high and low vigor, respectively. Both lots were placed in desiccators with a high relative humidity to hydrate and at 15 and 25 °C until levels of 10, 15, 20 and 25% moisture levels in seeds were reached. The seed cotyledons were analyzed for the quantity of monosaccharides and enzyme activity. The control had higher concentrations of xylose and rhamnose, which decreased during hydration until the 15% level was reached, after which concentrations increased again in both lots. Lot I, with a superior quality, showed higher glucose synthesis and degradation during seed hydration. Both enzymes were pre-existing since activity was already present in the seeds without imbibition. The polygalacturonase enzyme increased and the α-galactosidase enzyme remained relatively constant during seed hydration.

scholarly journals Synthesis and degradation of phosphoenolpyruvate carboxylase in rat liver and adipose tissue. Changes during a starvation–re-feeding cycle

1973 ◽  
Vol 134 (2) ◽  
pp. 445-453 ◽  
Author(s):  
M. F. Hopgood ◽  
F. J. Ballard ◽  
Lea Reshef ◽  
R. W. Hanson
Keyword(s):  
Adipose Tissue ◽  
Total Synthesis ◽  
Phosphoenolpyruvate Carboxylase ◽  
Degradation Rate ◽  
Relative Rate ◽  
Enzyme Synthesis ◽  
Starvation Period ◽  
Feeding Cycle ◽  
Tissue Changes ◽  
Synthesis And Degradation

A specific antibody against liver cytosol phosphoenolpyruvate carboxylase (EC 4.1.1.32) was used to isolate the enzyme from liver and adipose tissue. With this technique we have shown that phosphoenolpyruvate carboxylase synthesis in starved rats accounts for 3% of the total synthesis of cytosol protein in each tissue. Re-feeding starved animals decreases this relative rate of phosphoenolpyruvate carboxylase synthesis to 0.2% and 1% respectively in liver and adipose tissue, and the activity of the enzyme in each tissue is decreased to 25% of the starvation value. An additional starvation period is accompanied by an increased rate of enzyme synthesis, but the response to starvation is considerably slower than that caused by re-feeding. The degradation rate of phosphoenolpyruvate carboxylase is also subject to regulation. Thus re-feeding starved animals decreases the half-life of the enzyme in liver from 13h to 5.2h, but the rapid rate of degradation is maintained at least during the first 20h of subsequent starvation. Only slight changes in the degradation rate of phosphoenolpyruvate carboxylase are found in adipose tissue. We conclude that the large alterations in the rate of enzyme synthesis during a starvation–re-feeding cycle are the major cause of fluctuations in activity.

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