scholarly journals CYTOCHEMICAL STUDIES ON HYDROLYSIS OF CARBAMOYL PHOSPHATE IN RAT LIVER

1968 ◽  
Vol 1 (2) ◽  
pp. 79-94 ◽  
Author(s):  
AKIRA MIZUTANI ◽  
HAJIME FUJITA
Keyword(s):  
Rat Liver ◽  
Carbamoyl Phosphate ◽  
Hydrolysis Of

scholarly journals Hydrolysis of Retinol Palmitate by Rat Liver

1966 ◽  
Vol 241 (1) ◽  
pp. 57-64 ◽  
Author(s):  
S. Mahadevan ◽  
N.I. Ayyoub ◽  
O.A. Roels
Keyword(s):  
Rat Liver ◽  
Hydrolysis Of

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.

scholarly journals The roles of phospholipase D and a GTP-binding protein in guanosine 5′-[γ-thio]triphosphate-stimulated hydrolysis of phosphatidylcholine in rat liver plasma membranes

1990 ◽  
Vol 272 (3) ◽  
pp. 749-753 ◽  
Author(s):  
K M Hurst ◽  
B P Hughes ◽  
G J Barritt
Keyword(s):  
Rat Liver ◽  
Phospholipase D ◽  
Plasma Membranes ◽  
Regulatory Protein ◽  
Gtp Binding ◽  
Liver Plasma Membranes ◽  
Low Concentrations ◽  
Rat Liver Plasma Membranes ◽  
Triton X ◽  
Hydrolysis Of

1. Guanosine 5′-[gamma-thio]triphosphate (GTP[S]) stimulated by 50% the rate of release of [3H]choline and [3H]phosphorylcholine in rat liver plasma membranes labelled with [3H]choline. About 70% of the radioactivity released in the presence of GTP[S] was [3H]choline and 30% was [3H]phosphorylcholine. 2. The hydrolysis of phosphorylcholine to choline and the conversion of choline to phosphorylcholine did not contribute to the formation of [3H]choline and [3H]phosphorylcholine respectively. 3. The release of [3H]choline from membranes was inhibited by low concentrations of SDS or Triton X-100. Considerably higher concentrations of the detergents were required to inhibit the release of [3H]phosphorylcholine. 4. Guanosine 5′-[beta gamma-imido]triphosphate and guanosine 5′-[alpha beta-methylene]triphosphate, but not adenosine 5′-[gamma-thio]-triphosphate, stimulated [3H]choline release to the same extent as did GTP[S]. The GTP[S]-stimulated [3H]choline release was inhibited by guanosine 5′-[beta-thio]diphosphate, GDP and GTP but not by GMP. 5. It is concluded that, in rat liver plasma membranes, (a) GTP[S]-stimulated hydrolysis of phosphatidylcholine is catalysed predominantly by phospholipase D with some contribution from phospholipase C, and (b) the stimulation of phosphatidylcholine hydrolysis by GTP[s] occurs via a GTP-binding regulatory protein.

scholarly journals Anomeric specificity of d-glucose phosphorylation by rat liver glucose-6-phosphatase

1989 ◽  
Vol 261 (2) ◽  
pp. 509-513
Author(s):  
R Ramirez ◽  
D Zähner ◽  
G Marynissen ◽  
A Sener ◽  
W J Malaisse
Keyword(s):  
Rat Liver ◽  
Glycogen Synthesis ◽  
Liver Microsomes ◽  
Diabetic Rats ◽  
Enzymic Activity ◽  
Rat Liver Microsomes ◽  
Maximal Velocity ◽  
Carbamoyl Phosphate ◽  
Glucose Phosphorylation ◽  
Anomeric Specificity

The anomeric specificity of D-glucose phosphorylation by hepatic glucose-6-phosphatase was examined in rat liver microsomes incubated in the presence of carbamoyl phosphate. At 10 degrees C, the Km for the equilibrated hexose and phosphate donor was close to 56 mM and 11 mM, respectively. The enzymic activity, which was increased in diabetic rats, was about 40% lower in untreated than in sonicated microsomes. No anomeric difference in affinity was found in sonicated microsomes. In untreated microsomes, however, the Km for beta-D-glucose was slightly lower than that for alpha-D-glucose. The maximal velocity was higher with beta- than alpha-D-glucose in both untreated and sonicated microsomes. These data indicate that the phosphotransferase activity of glucose-6-phosphatase cannot account for the higher rate of glycolysis and glycogen synthesis found in hepatocytes exposed to alpha- rather than beta-D-glucose.

scholarly journals Accumulation of amino acids by the perfused rat liver in the presence of ethanol

1973 ◽  
Vol 134 (3) ◽  
pp. 697-705 ◽  
Author(s):  
Hans A. Krebs ◽  
Reginald Hems ◽  
Patricia Lund
Keyword(s):  
Amino Acids ◽  
Rat Liver ◽  
Major Effect ◽  
Major Product ◽  
Control Mechanisms ◽  
Perfused Rat Liver ◽  
Carbamoyl Phosphate ◽  
Lactate Formation ◽  
Gluconeogenesis From Alanine ◽  
Almost All

1. The rate of gluconeogenesis from alanine in the perfused rat liver is affected by the presence of other metabolizable substances, especially fatty acids, ornithine and ethanol. Gluconeogenesis is accelerated by oleate and by ornithine. When both oleate and ornithine were present the acceleration was greater than expected on the basis of mere additive effects. 2. Much NH3 and some urea were formed from alanine when no ornithine was added. With ornithine almost all the nitrogen released from alanine appeared as urea. 3. Lactate was a major product of alanine metabolism. Addition of oleate, and especially of oleate plus ornithine, decreased lactate formation. 4. Ethanol had no major effect on gluconeogenesis from alanine when this was the sole added precursor. Gluconeogenesis was strongly inhibited (87%) when oleate was also added, but ethanol greatly accelerated gluconeogenesis when ornithine was added together with alanine. 5. In the absence of ethanol the alanine carbon and alanine nitrogen removed were essentially recovered in the form of glucose, lactate, pyruvate, NH3 and urea. 6. In the presence of ethanol the balance of both alanine carbon and alanine nitrogen showed substantial deficits. These deficits were largely accounted for by the formation of aspartate and glutamine, the formation of which was increased two- to three-fold. 7. When alanine was replaced by lactate plus NH4Cl, ethanol also caused a major accumulation of amino acids, especially of aspartate and alanine. 8. Earlier apparently discrepant results on the effects of ethanol on gluconeogenesis from alanine are explained by the fact that under well defined conditions ethanol can inhibit, or accelerate, or be without major effect on the rate of gluconeogenesis. 9. It is pointed out that in the synthesis of urea through the ornithine cycle half of the nitrogen must be supplied in the form of asparate and half in the form of carbamoyl phosphate. The accumulation of aspartate and other amino acids suggests that ethanol interferes with the control mechanisms which regulate the stoicheiometric formation of aspartate and carbamoyl phosphate.

Decreased Hydrolysis of Solvent-Derived Oxa Acyl-CoA by Rat Liver Acyl-CoA Hydrolases

2000 ◽  
Vol 28 (5) ◽  
pp. A437-A437
Author(s):  
S. D. Panuganti ◽  
J. R. Frybarger ◽  
K. H. Moore
Keyword(s):  
Rat Liver ◽  
Hydrolysis Of
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