Stimulation of rat liver phenylalanine hydroxylase activity by derivatives of vitamin E

1972 ◽  
Vol 48 (5) ◽  
pp. 1185-1191 ◽  
Author(s):  
David A. Brase ◽  
Thomas C. Westfall
Keyword(s):  
Vitamin E ◽  
Rat Liver ◽  
Phenylalanine Hydroxylase ◽  
Hydroxylase Activity ◽  
Derivatives Of ◽  
Stimulation Of

Comparison of Different Methods for the Determination of Phenylalanine Hydroxylase Activity in Rat Liver and Euglena gracilis

1984 ◽  
Vol 39 (7-8) ◽  
pp. 728-733 ◽  
Author(s):  
Rita M. Fink ◽  
Erich F. Elstner
Keyword(s):  
Rat Liver ◽  
Euglena Gracilis ◽  
Phenylalanine Hydroxylase ◽  
Hplc Method ◽  
Enzymic Activity ◽  
Hydroxylase Activity ◽  
Product Separation ◽  
Tyrosine Concentration ◽  
Layer Chromatography

Abstract Three different methods for the determination of phenylalanine hydroxylase activity have been compared: a) Differential photometric assay of the increase in tyrosine concentration in the presence of phenylalanine; b) Product separation by thin layer chromatography and scintillation counting of the [14C]tyrosine formed;c) HPLC separation and spectrofluorometric quantification of derivatized amino acids. A comparison of the activities of phenylalanine hydroxylase in rat liver and Euglena gracilis clearly showed that only rat liver contains this enzymic activity as shown by methods b) and c) although pseudo-activity of Euglena gracilis preparations was found during the spectrophotometric test a). The HPLC method proved to be the fastest, most reliable and convenient method for direct tyrosine determination and thus for measuring phenylalanine hydroxylase activity.

Effect of glucagon on hepatic phenylalanine hydroxylase in vivo

1985 ◽  
Vol 5 (6) ◽  
pp. 463-467 ◽  
Author(s):  
Edel Beirne ◽  
Michael P. Carty ◽  
John Donlon
Keyword(s):  
Phenylalanine Hydroxylase ◽  
High Protein Diet ◽  
Physiological Changes ◽  
Phosphate Content ◽  
Hydroxylase Activity ◽  
Human Phenylalanine Hydroxylase ◽  
Stimulation Of ◽  
Glucagon Concentration

Moderate doses of glucagon (20 μg/kg I.V.) are sufficient to stimulate rat hepatic phenylalanine hydroxylase in vivo. In addition, the stimulation of the tetrahydrobiopterin-dependent phenylalanine hydroxylase activity in livers of animals fed on a high-protein diet has been correlated with an elevated phosphate content. The tetrahydrobiopterin-dependent hydroxylase activity in these animals can be further elevated by glucagon-stimulated phosphorylation. These results indicate that physiological changes in glucagon concentration modulate rat liver phenylalanine hydroxylase activity in vivo. The current understanding of the role of phosphorylation in regulating human phenylalanine hydroxylase is also considered.

Influence of amino acids on rat liver phenylalanine hydroxylase activity

1964 ◽  
Vol 206 (2) ◽  
pp. 341-344 ◽  
Author(s):  
R. A. Freedland ◽  
M. C. Krakowski ◽  
Harry A. Waisman
Keyword(s):  
Amino Acids ◽  
Enzyme Activity ◽  
Rat Liver ◽  
Phenylalanine Hydroxylase ◽  
Marked Decrease ◽  
Hydroxylase Activity ◽  
Short Term ◽  
Ad Libitum

The influence of oral and of injected amino acids on rat liver phenylalanine hydroxylase activity has been studied in both short-term and extended experiments. Phenylalanine added to the diet in moderate amounts ordinarily causes an increase in enzyme activity, but when excess phenylalanine was included in the diet, it caused a marked decrease in the enzyme activity in rats fed ad libitum. Tryptophan or tyrosine added to the diet in the absence of added phenylalanine increased the enzyme activity in these rats. Excess tryptophan, but not tyrosine, could counteract the effect of phenylalanine on this enzyme after an 18-hr fast. There were dramatic differences in phenylalanine hydroxylase activity when various amino acids were injected. Injection of tryptophan or glycine decreased the phenylalanine hydroxylase activity in rat liver. Injections of other amino acids, notably phenylalanine and tyrosine, had no effect on the phenylalanine hydroxylase activity 5 hr after injection.

Effect of age, sex, and nutrition on liver phenylalanine hydroxylase activity in rats

1962 ◽  
Vol 202 (1) ◽  
pp. 145-148 ◽  
Author(s):  
R. A. Freedland ◽  
M. C. Krakowski ◽  
Harry A. Waisman
Keyword(s):  
Enzyme Activity ◽  
Rat Liver ◽  
Phenylalanine Hydroxylase ◽  
Total Amino Acid ◽  
Rapid Decline ◽  
Female Rat ◽  
Hydroxylase Activity ◽  
Adult Age ◽  
Number Of Factors ◽  
Amino Acid Intake

This study provides data on a number of factors that influence phenylalanine hydroxylase activity in rat liver. By means of a method which utilizes crude liver homogenates, the enzyme activity was determined in rat liver obtained from early embryos to 150-day-old animals. The activity increases with age to a maximum at the young adult age of 50–60 days and then declines. The most rapid increase in activity was found between 18–21 days. The female rat livers show a rapid decline in activity with increasing age, then stabilize at a lower activity than males after maturity is reached. Fasting causes a marked drop in activity, and diets deficient in phenylalanine cause a decrease in the enzyme activity. High casein diets, which increase the phenylalanine and total amino acid intake, had no apparent effect on the level of enzyme activity.

Stimulation of hepatic phenylalanine hydroxylase activity but not Pah-mRNA expression upon oral loading of tetrahydrobiopterin in normal mice

2005 ◽  
Vol 86 ◽  
pp. 153-155 ◽  
Author(s):  
Rossana Scavelli ◽  
Zhaobing Ding ◽  
Nenad Blau ◽  
Jan Haavik ◽  
Aurora Martínez ◽  
...  
Keyword(s):  
Mrna Expression ◽  
Phenylalanine Hydroxylase ◽  
Hydroxylase Activity ◽  
Stimulation Of
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