Adenosine phosphorylase activity as distinct from inosine-guanosine phosphorylase activity in sarcoma 180 cells and rat liver

1976 ◽  
Vol 422 (1) ◽  
pp. 15-28 ◽  
Author(s):  
Ashok Y. Divekar
Keyword(s):  
Rat Liver ◽  
Sarcoma 180 ◽  
Phosphorylase Activity

Phosphorylase Activity of Primary Rat Liver Cancer

Nature ◽  
1958 ◽  
Vol 181 (4608) ◽  
pp. 547-548 ◽  
Author(s):  
A. A. HADJIOLOV ◽  
K. I. DANCHEVA
Keyword(s):  
Liver Cancer ◽  
Rat Liver ◽  
Phosphorylase Activity

The relationship between Mg2+-stimulated ATPase activity and glycogen content in rat liver

1969 ◽  
Vol 47 (3) ◽  
pp. 339-345 ◽  
Author(s):  
B. Rubenstein ◽  
P. G. Scholefield
Keyword(s):  
Enzyme Activity ◽  
Atpase Activity ◽  
Rat Liver ◽  
Glycogen Content ◽  
Phosphorylase Activity ◽  
Tumor Bearing ◽  
Physical Association ◽  
The Relationship

During starvation there is an increase in the ATPase activity of a postmitochondrial fraction of rat liver. The increase is relatively specific for ATP and there is no change in the Na+,K+-stimulated ATPase activity. A corresponding increase in ATPase activity is found on pretreatment of the rat with glucagon and in tumor-bearing animals. The increase has been correlated with increase in phosphorylase activity and decrease in glycogen content under in vivo and in vitro conditions. Treatment of fasted animals with glucose or sucrose restores the glycogen content and diminishes the ATPase activity to normal levels, but puromycin is without effect. It is proposed that a physical association of glycogen with Mg2+-stimulated ATPase activity prevents the enzyme activity from being expressed.

Effect of glycogenolytic agents on phosphorylase activity of perfused rat liver

1965 ◽  
Vol 208 (2) ◽  
pp. 317-323 ◽  
Author(s):  
Robert A. Levine
Keyword(s):  
Rat Liver ◽  
Cyclic Nucleotide ◽  
Adenine Nucleotides ◽  
Adenosine Monophosphate ◽  
Isolated Perfused Rat Liver ◽  
Perfused Rat Liver ◽  
Adrenocorticotrophic Hormone ◽  
Phosphorylase Activity ◽  
Glycogen Breakdown ◽  
Intact Rats

The effect of glycogenolytic agents on phosphorylase activity has been studied in the isolated perfused rat liver. Evidence is presented showing that endoportal administration of 10–6m glucagon, 10–5 m epinephrine, and 10–3 M cyclic 3',5'-adenosine monophosphate (3',5'-AMP) induced glycogenolysis, hyperglycemia, and increase in liver phosphorylase activity, usually within 1 hr after the onset of infusion. ATP, 10–3m, also caused glycogenolysis, but the onset was slower than with the cyclic nucleotide, and phosphorylase activation was inconstant Hyperglycemic effects of these two adenine nucleotides were also demonstrated in intact rats. Anoxia and hypoxia caused substantial glycogenolysis but did not stimulate phosphorylase activity, implying that some other mechanism accounts for the glycogen breakdown induced by reduced oxygen tension. Glycogenolysis and phosphorylase activation were not produced by administration of 10–2 M 5'-AMP, 10–4 M isoproterenol, adrenocorticotrophic hormone, or insulin.

Uridine phosphorylase activity of isolated plasma membranes of rat liver

1977 ◽  
Vol 55 (5) ◽  
pp. 528-533 ◽  
Author(s):  
Ratna Bose ◽  
Esther W. Yamada
Keyword(s):  
Rat Liver ◽  
Plasma Membranes ◽  
Enrichment Factors ◽  
Marker Enzyme ◽  
Differential Centrifugation ◽  
Uridine Phosphorylase ◽  
Phosphorylase Activity ◽  
Subcellular Organelles ◽  
Liver Homogenates ◽  
Triton X

Plasma membranes were isolated from rat liver homogenates either by differential centrifugation or by fractionation in discontinuous sucrose density gradients. Both membrane preparations contained about 17% of the total uridine phosphorylase (EC 2.4.2.3) activity and 44% of the total 5′-nucleotidase (EC 3.1.3.5). The enrichment factor for uridine phosphorylase in the fractions prepared by differential centrifugation was about 2.8 and by the gradient method, as much as 11.0; the respective enrichment factors for 5′-nucleotidase were 1.8 and 9.5. Uridine phosphorylase activity of isolated plasma membrane fractions was stimulated 2.5-fold by 0.1% Triton X-100. Unlike the cytosol enzyme, uridine phosphorylase of plasma membranes showed little or no deoxyuridine-cleaving activity. Contamination of the membrane fractions by thymidine phosphorylase (EC 2.4.2.4) of the cytosol was negligible.The other subcellular organelles obtained by either procedure and characterized by marker enzyme activities were found not to contain significant uridine phosphorylase activity; the cytosol fractions contained just over 70% of the total uridine phosphorylase activity with an enrichment of only about 2.8-fold. The activity of the cytosol enzyme was not stimulated by Triton X-100.

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