scholarly journals The function of subcellular fractions in the oxidation of glutathione in rat liver homogenate

1970 ◽  
Vol 117 (5) ◽  
pp. 951-956 ◽  
Author(s):  
P. C. Jocelyn
Keyword(s):  
Uric Acid ◽  
Xanthine Oxidase ◽  
Rat Liver ◽  
Liver Homogenate ◽  
No Oxidation ◽  
Urate Oxidase ◽  
Supernatant Fraction ◽  
Endogenous Substrate ◽  
Additional Protein ◽  
Microsome Fraction

1. The aerobic loss of GSH added to the supernatant fraction from rat liver is much increased by including the microsome fraction, which both inhibits the concurrent reduction of the GSSG formed and also augments the net oxidation rate. 2. Oxidation occurs with a mixture of dialysed supernatant and a protein-free filtrate; the latter is replaceable by hypoxanthine and the former by xanthine oxidase, whereas fractions lacking this enzyme give no oxidation. 3. In all these instances augmentation occurs with microsomes, with fractions having urate oxidase activity and with the purified enzyme; uric acid and microsomes alone also support the oxidation. 4. Evidence implicating additional protein factors is discussed. 5. It is suggested that GSH oxidation by homogenate is linked through glutathione peroxidase to the reaction of endogenous substrate with supernatant xanthine oxidase and of the uric acid formed with peroxisomal urate oxidase.

scholarly journals Chain extension of ribonucleic acid by enzymes from rat liver cytoplasm

1968 ◽  
Vol 109 (4) ◽  
pp. 485-494 ◽  
Author(s):  
N. M. Wilkie ◽  
R. M. S. Smellie
Keyword(s):  
Rat Liver ◽  
Alkaline Hydrolysis ◽  
Actinomycin D ◽  
Chain Extension ◽  
Supernatant Fraction ◽  
Inorganic Pyrophosphate ◽  
Optimum Ph ◽  
Microsome Fraction ◽  
Hydrolysis Of ◽  
Generating System

1. The 105000g supernatant fraction of rat liver catalyses the incorporation of ribonucleotides from ribonucleoside triphosphates into polyribonucleotide material. The reaction requires Mg2+ ions and is enhanced by the addition of an ATP-generating system and RNA, ATP, UTP and CTP but not GTP are utilized in this reaction. In the case of UTP, the product is predominantly a homopolymer containing 2–3 uridine residues, and there is evidence that these may be added to the 3′-hydroxyl ends of RNA or oligoribonucleotide primers. 2. The microsome fraction of rat liver incorporates ribonucleotides from ATP, GTP, CTP and UTP into polyribonucleotide material. This reaction requires Mg2+ ions and is enhanced slightly by the addition of an ATP-generating system, and by RNA but not DNA. Supplementation of the reaction mixture with the three complementary ribonucleoside 5′-triphosphates greatly increases the utilization of a single labelled ribonucleoside 5′-triphosphate. The optimum pH is in the range 7·0–8·5, and the reaction is strongly inhibited by inorganic pyrophosphate and to a much smaller degree by inorganic orthophosphate. It is not inhibited by actinomycin D or by deoxyribonuclease. In experiments with [32P]UTP in the absence of ATP, GTP and CTP, 80–90% of 32P was recovered in UMP-2′ or −3′ after alkaline hydrolysis of the reaction product. When the reaction mixture was supplemented with ATP, GTP and CTP, however, about 40% of the 32P was recovered in nucleotides other than UMP-2′ or −3′. Although the reactions seem to lead predominantly to the synthesis of homopolymers, the possibility of some formation of some heteropolymer is not completely excluded.

Biosynthesis of 1,2-3H and 4-14C steroid sulfates of high specific activity

1970 ◽  
Vol 48 (1) ◽  
pp. 148-150 ◽  
Author(s):  
J. Torday ◽  
G. Hall ◽  
M. Schweitzer ◽  
C. J. P. Giroud
Keyword(s):  
Rat Liver ◽  
Specific Activity ◽  
Liver Homogenate ◽  
High Specific Activity ◽  
Supernatant Fraction ◽  
Metabolic Studies

A supernatant fraction of rat liver homogenate enriched with ATP was used for the biosynthesis of the ester sulfates of several 3H and 14C steroids of the pregn-4-ene series. The method provides a simple means to prepare steroid sulfates of high specific activity for use in either metabolic studies or as reference compounds in the quantification of such conjugates by isotope assays.

METHYLATION OF THE 3-OH POSITION OF CATECHOL ACIDS BY RAT LIVER AND KIDNEY PREPARATIONS

1958 ◽  
Vol 36 (5) ◽  
pp. 491-497 ◽  
Author(s):  
J. Pellerin ◽  
A. D'Iorio
Keyword(s):  
Enzymatic Activity ◽  
Rat Liver ◽  
Paper Chromatography ◽  
Reduced Glutathione ◽  
Liver Homogenate ◽  
Supernatant Fraction ◽  
Hydroxybenzoic Acid ◽  
Dihydroxybenzoic Acid ◽  
Kidney Homogenate ◽  
Liver And Kidney

3,4-Dihydroxybenzoic acid, 3,4-dihydroxyphenylacetic acid, 3,4-dihydroxymandelic acid, and 3,4-dihydroxycinnamic acid were separately incubated with L-methionine-methyl-C14 in the presence of rat liver or kidney homogenate. In each case, the radioactive metabolite separated by paper chromatography was found to have migrating properties similar to those of the 3-methoxy-4-hydroxyphenolic acid. This reaction was enhanced by the addition of ATP, Mg++, and reduced glutathione. When 3-hydroxybenzoic acid was incubated in this medium no methylated derivative was obtained. Preliminary experiments indicated that the enzymatic activity was contained mostly in the supernatant fraction. It was also noted that liver homogenate was much more active than kidney homogenate in methylating catechol acids.

METHYLATION OF THE 3-OH POSITION OF CATECHOL ACIDS BY RAT LIVER AND KIDNEY PREPARATIONS

1958 ◽  
Vol 36 (1) ◽  
pp. 491-497 ◽  
Author(s):  
J. Pellerin ◽  
A. D'Iorio
Keyword(s):  
Enzymatic Activity ◽  
Rat Liver ◽  
Paper Chromatography ◽  
Reduced Glutathione ◽  
Liver Homogenate ◽  
Supernatant Fraction ◽  
Hydroxybenzoic Acid ◽  
Dihydroxybenzoic Acid ◽  
Kidney Homogenate ◽  
Liver And Kidney

3,4-Dihydroxybenzoic acid, 3,4-dihydroxyphenylacetic acid, 3,4-dihydroxymandelic acid, and 3,4-dihydroxycinnamic acid were separately incubated with L-methionine-methyl-C14 in the presence of rat liver or kidney homogenate. In each case, the radioactive metabolite separated by paper chromatography was found to have migrating properties similar to those of the 3-methoxy-4-hydroxyphenolic acid. This reaction was enhanced by the addition of ATP, Mg++, and reduced glutathione. When 3-hydroxybenzoic acid was incubated in this medium no methylated derivative was obtained. Preliminary experiments indicated that the enzymatic activity was contained mostly in the supernatant fraction. It was also noted that liver homogenate was much more active than kidney homogenate in methylating catechol acids.

scholarly journals A Biochemical and Morphological Study of Rat Liver Microsomes

1960 ◽  
Vol 7 (3) ◽  
pp. 547-557 ◽  
Author(s):  
Y. Moulé ◽  
C. Rouiller ◽  
J. Chauveau
Keyword(s):  
Rat Liver ◽  
Microsomal Fraction ◽  
Sucrose Solution ◽  
Liver Microsomes ◽  
Liver Homogenate ◽  
Sodium Deoxycholate ◽  
Point Of View ◽  
Rat Liver Microsomes ◽  
Experimental Conditions ◽  
Microsome Fraction

Microsomes isolated by differential centrifugation from a rat liver homogenate in 0.88 M sucrose solution have been studied from the biochemical and morphological point of view. 1. Under these experimental conditions, the "total microsome" fraction was obtained by centrifuging the cytoplasmic extract free of nuclei and mitochondria, for 3 hours at 145,000 g. Morphologically, the total microsomes consist mainly of "rough-surfaced membranes" and "smooth" ones. 2. The total microsomes have been divided into 2 subfractions so that the 1st microsomal fraction contains the "rough" vesicles (2 hours centrifugation at 40,000 g) while the 2nd microsomal fraction consists essentially of smooth vesicles, free particles, and ferritin (centrifugation of the supernatant at 145,000 g for 3 hours). 3. By the action of 0.4 per cent sodium deoxycholate in 0.88 M sucrose, it was possible to obtain a pellet for each of the 2 fractions which consisted of dense particles, rich in RNA, poor in lipids, and which represented about 50 to 60 percent of the RNA and 10 to 15 per cent of the proteins. The results have been discussed taking into consideration the hypothesis of the presence of RNA in the membranes of microsomal vesicles.

scholarly journals The enzymic oxidation of glutathione in rat liver homogenates

1970 ◽  
Vol 117 (5) ◽  
pp. 947-949 ◽  
Author(s):  
P. C. Jocelyn
Keyword(s):  
Xanthine Oxidase ◽  
Rat Liver ◽  
Aerobic Oxidation ◽  
Liver Homogenate ◽  
Enzymic Oxidation ◽  
Liver Homogenates

1. The aerobic oxidation of GSH and other thiols by rat liver homogenate is abolished either by previous dialysis or by removal of the proteins but is restored by a mixture of the protein-free filtrate and the dialysed homogenate. 2. The oxidation is prevented by previously heating the dialysed homogenate but not the protein-free filtrate and also by known inhibitors of xanthine oxidase. 3. A similar oxidation occurs with hypoxanthine in place of of protein-free filtrate.

scholarly journals Biosynthesis of cyclopropyl long-chain fatty acids from cyclopropanecarboxylic acid by mammalian tissues in vitro

1968 ◽  
Vol 109 (3) ◽  
pp. 449-455 ◽  
Author(s):  
W. G. Duncombe ◽  
T. J. Rising
Keyword(s):  
Fatty Acids ◽  
Rat Liver ◽  
Liver Homogenate ◽  
Supernatant Fraction ◽  
Long Chain Fatty Acids ◽  
Straight Chain ◽  
Cyclopropanecarboxylic Acid ◽  
Mammalian Tissues ◽  
Chain Fatty Acids

1. Radioactivity from cyclopropane[14C]carboxylic acid is incorporated into fatty acids in vitro by rat and guinea-pig adipose tissue, by rat liver slices and by the supernatant fraction of rat liver homogenate. 2. The labelled acids are different from endogenous straight-chain fatty acids, and evidence is produced that they consist of a cyclopropyl ring in the ω-position, the remainder of the chain being built up from C2 units (not derived from cyclopropanecarboxylic acid) in the normal way via the malonate pathway. 3. It is suggested that these unnatural acids have some metabolic effect related to the hypoglycaemic action of cyclopropanecarboxylic acid.

Cholesterol metabolism and vitamin B6. I. Hepatic cholesterogenesis and pyridoxine deficiency

1969 ◽  
Vol 47 (6) ◽  
pp. 631-635 ◽  
Author(s):  
P. J. Lupien ◽  
C. M. Hinse ◽  
M. Avery
Keyword(s):  
Rat Liver ◽  
High Speed ◽  
Cholesterol Metabolism ◽  
Reductase Activity ◽  
Liver Microsomes ◽  
Liver Homogenate ◽  
Supernatant Fraction ◽  
Liver Cholesterol ◽  
Pyridoxine Deficiency ◽  
Hepatic Cholesterogenesis

Hepatic cholesterogenesis was studied in pair-fed and pyridoxine-deficient rats as well as in rat liver homogenate systems. Crossover of various subcellular components from pair-fed homogenates into pyridoxine-deficient homogenate systems and vice versa was also done.On 8 weeks of pyridoxine deficiency, acetate-14C incorporation rates into liver cholesterol increased by a factor of approximately 10. The same phenomenon was observed with the total liver homogenate systems.Pyridoxine deficiency does not appear to affect HMG-CoA reductase activity of pyridoxine-deficient liver microsomes sufficiently to explain the rapid acetate-1-14C incorporation rates in this same tissue. The activating system(s) responsible for the 10-fold increase in acetate-14C incorporation rates into pyridoxine-deficient rat liver cholesterol appears to be located in the high-speed supernatant fraction. Other subcellular components such as lysosomes and mitochondria are probably implicated to some extent in this phenomenon. The results indicate that vitamin B6 is necessary for normal hepatic cholesterogenesis in the rat.The significance of these findings and the possible relationship between these factors are discussed.

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