scholarly journals Effects of thyroxine on the synthesis of folate coenzymes in rat liver

1970 ◽  
Vol 116 (2) ◽  
pp. 217-221 ◽  
Author(s):  
P. Pasquali ◽  
L. Landi ◽  
C. Bovina ◽  
M. Marchetti
Keyword(s):  
Rat Liver ◽  
Chronic Administration ◽  
Serine Hydroxymethyltransferase ◽  
Acute Administration ◽  
Formyltetrahydrofolate Synthetase ◽  
Derivatives Of

1. The effects of thyroidectomy and of ‘acute’ and ‘chronic’ administration of thyroxine on the synthesis of folate coenzymes were studied by determining the liver contents of folate active derivatives and the enzymic activities involved in their biosynthesis. The effect of thyroxine on the same enzymes in vitro was also studied. 2. In thyroidectomized rats the liver contents of folate coenzymes did not change except for a slight decrease in the contents of 5-formyltetrahydrofolate and tetrahydrofolate compared with those in control rats. 3. In the same animals serine hydroxymethyltransferase and formyltetrahydrofolate synthetase activities decreased markedly. 4. The ‘chronic’ administration of thyroxine to thyroidectomized rats caused more evident variations in the liver contents of folate coenzymes and in particular a decrease in the contents of 5-formyltetrahydrofolate, tetrahydrofolate, 5(or 10)-formyl derivatives of tetrahydropteroylpolyglutamate and of 5(or 10)-formyl derivatives of pteroylpolyglutamate. 5. The enzymic activities did not show significant variations. 6. The ‘acute’ administration of thyroxine caused changes in the liver contents of some folate derivatives such as 10-formyldihydrofolate, 10-formylfolate, tetrahydrofolate and the 10-formyl derivative of dihydropteroylpolyglutamate. In these animals also the enzymic activities were unchanged. 7. No effect of thyroxine on enzymic activities in vitro was observed.

scholarly journals The association in vitro of polyribosomes with ribonuclease-treated derivatives of hepatic rough endoplasmic reticulum. Characteristics of the membrane binding sites and factors influencing association

1971 ◽  
Vol 125 (1) ◽  
pp. 67-79 ◽  
Author(s):  
T. K. Shires ◽  
L. Narurkar ◽  
H. C. Pitot
Keyword(s):  
Rat Liver ◽  
Binding Sites ◽  
Binding Capacity ◽  
Trypsin Treatment ◽  
Partial Removal ◽  
Adult Rat ◽  
Microsomal Membranes ◽  
Derivatives Of ◽  
Membrane Binding Sites

1. Pancreatic ribonuclease in dilute EDTA has been shown to condition rough-microsomal membranes from adult rat liver to accept exogenously added rat liver polyribosomes in vitro at 0–4°C. Treated smooth membranes would not significantly interact with polyribosomes. 2. The conditioning process decreased the membrane RNA content and removed polyribosomes from vesicle surfaces as viewed electron-microscopically. 3. Binding to these conditioned membranes was shown to be uninfluenced by changes of temperature (0–37°C) and pH (6.9–7.8) or the presence of cell sap, but was inhibited by increasing the concentration of potassium chloride. 4. Possession of a polyribosome-binding capacity by conditioned rough membranes was not dependent on adventitious materials that could be dislodged by high ionic strengths. 5. Trypsin treatment under mild conditions destroyed the binding capacity of ribonuclease-conditioned rough membranes. 6. A 2–10S residual RNA was recovered from ribonuclease-conditioned membranes, but its partial removal had no effect on the capacity of membranes to accept polyribosomes. However, some role for this residual RNA in attaching polyribosomes could not be discounted. 7. Evidence is considered that polyribosome-binding sites are intrinsic features of conditioned membranes isolated from rough-microsomal fractions, and that long-range ionic bonding is a primary factor in polyribosome interaction with these binding sites.

scholarly journals Regulation of C1 metabolism by l-methionine in Saccharomyces cerevisiae

1972 ◽  
Vol 130 (3) ◽  
pp. 773-783 ◽  
Author(s):  
K. L. Lor ◽  
E. A. Cossins
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Methylenetetrahydrofolate Reductase ◽  
Deae Cellulose ◽  
Serine Hydroxymethyltransferase ◽  
C1 Metabolism ◽  
Formyltetrahydrofolate Synthetase ◽  
Feeding Experiments ◽  
Cellulose Column ◽  
Homocysteine Methyltransferase

1. The concentrations of folate derivatives in aerobic cultures of Saccharomyces cerevisiae (A.T.C.C. 9763) were determined by microbiological assay employing Lactobacillus casei (A.T.C.C. 7469) and Pediococcus cerevisiae (A.T.C.C. 8081). Cells cultured in media lacking l-methionine contained higher concentrations of folate derivatives than cells grown in the same media supplemented with 2.5μmol of l-methionine/ml. The concentrations of highly conjugated derivatives were also decreased by supplementing the growth medium with l-methionine. 2. DEAE-cellulose column chromatography of extracts prepared from cells grown under these conditions revealed that the concentrations of methylated tetrahydrofolates were drastically decreased by the methionine supplement. Smaller decreases were also observed in the concentrations of formylated and unsubstituted derivatives. 3. The concentrations of four enzymes of C1 metabolism were compared after 6h of growth in the presence and in the absence of l-methionine (2.5μmol/ml). The specific activities of formyltetrahydrofolate synthetase, methylenetetrahydrofolate reductase and serine hydroxymethyltransferase were not altered by this treatment but that of 5-methyltetrahydrofolate–homocysteine methyltransferase was decreased by approx. 65% when l-methionine was supplied. The activities of 5-methyltetrahydrofolate–homocysteine methyltransferase, serine hydroxymethyltransferase and formyltetrahydrofolate synthetase were not appreciably altered by l-methionine in vitro. In contrast this amino acid was found to inhibit the activity of methylenetetrahydrofolate reductase. 4. Feeding experiments employing sodium [14C]formate indicated that cells grown in the presence of exogenous methionine, although having less ability to convert formate into methionine, readily incorporated 14C into serine and the adenosyl moiety of S-adenosylmethionine. 5. It is suggested that exogenous l-methionine controls C1 metabolism in Saccharomyces principally by regulation of methyl-group biogenesis within the folate pool.

Inhibitions by E-64 Derivatives of Rat Liver Cathepsin B and Cathepsin L In Vitro and In Vivo 1

1980 ◽  
Vol 88 (6) ◽  
pp. 1805-1811 ◽  
Author(s):  
Seiichi HASHIDA ◽  
Takae TOWATARI ◽  
Eiki KOMINAMI ◽  
Nobuhiko KATUNUMA
Keyword(s):  
Rat Liver ◽  
Cathepsin B ◽  
Cathepsin L ◽  
Derivatives Of

Metabolism of K-region derivatives of 1-nitropyrene by rat liver in vitro

1988 ◽  
Vol 9 (2) ◽  
pp. 255-258 ◽  
Author(s):  
Ajit K. Roy ◽  
Karam El-Bayoumy ◽  
Stephen S. Hecht
Keyword(s):  
Rat Liver ◽  
Derivatives Of

scholarly journals The effects of acute and chronic nicotine hydrogen (+)-tartrate administration and subsequent withdrawal on rat liver tryptophan pyrrolase activity and their comparison with those of morphine, phenobarbitone and ethanol

1975 ◽  
Vol 148 (3) ◽  
pp. 425-432 ◽  
Author(s):  
A A Badawy ◽  
M Evans
Keyword(s):  
Rat Liver ◽  
Acute Administration ◽  
Nicotine Treatment ◽  
Chronic Nicotine ◽  
Nicotine Administration ◽  
Hormonal Mechanism ◽  
Tryptophan Pyrrolase ◽  
Subsequent Withdrawal

Acute administration of nicotine hydrogen (+)-tartrate enhances the activity of rat liver tryptophan pyrrolase by a hormonal mechanism. Chronic nicotine treatment inhibits, and subsequent withdrawal enhances, the pyrrolase activity. The inhibition during chronic treatment is not due to a defective apoenzyme synthesis nor a decreased cofactor availability. Regeneration of liver NADP+ in vitro and in vivo reverses the inhibition. Chronic nicotine administration increases the liver NADPH concentration. The above effects of nicotine resemble to a remarkable degree those previously shown for morphine, phenobarbitone and ethanol. All effects are compared, and their possible significance in relation to drug dependence is discussed.

scholarly journals The regulation of rat liver tryptophan pyrrolase activity by reduced nicotinamide-adenine dinucleotide (phosphate). Experiments with glucose and nicotinamide

1976 ◽  
Vol 156 (2) ◽  
pp. 381-390 ◽  
Author(s):  
A A B Badawy ◽  
M Evans
Keyword(s):  
Drinking Water ◽  
Rat Liver ◽  
Nicotinamide Adenine Dinucleotide Phosphate ◽  
Chronic Administration ◽  
Glucose Effect ◽  
Tryptophan Pyrrolase ◽  
Subsequent Withdrawal ◽  
Phenazine Methosulphate

1. Chronic administration of glucose or nicotinamide in drinking water inhibits the activity of rat liver tryptophan pyrrolase, and subsequent withdrawal causes an enhancement. The enzyme activity is also inhibited by administration in drinking water of sucrose, but not fructose, which is capable of preventing the glucose effect. 2. The inhibition by glucose or nictinamide is not due to a defective apoenzyme synthesis nor a decreased cofactor availability. 3. The inhibition by nicotinamide is reversed by regeneration of liver NAD+ and NADP+ in vivo by administration of fructose, pyruvate or phenazine methosulphate. Inhibition by glucose is also reversed by the above agents and by NH4Cl. Reversal of inhibition by glucose or nicotinamide is also achieved in vitro by addition of NAD+ or NADP+. 4. Glucose or nicotinamide increases liver [NADPH]. [NADP+] is also increased by nicotinamide. [NADPH] is also increased by sucrose, but not by fructose, which prevents the glucose effect. Phenazine methosulphate prevents the increase in [NADPH] caused by both glucose and nicotinamide. 5. It is suggested that the inhibition of tryptophan pyrrolase activity by glucose or nicotinamide is mediated by both NADPH and NADH.

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