Biomaterial Database

The mechanism of caffeine-enhanced glucose stimulation of liver glycogen synthase phosphatase activity. 1986

D P Gilboe

Our report that glucose within its physiological range stimulates glycogen synthase phosphatase activity, provided an appropriate second effector is present, has been expanded. The nature of the stimulatory process, particularly the roles of glucose, and of caffeine which represents the potential second effectors, has been studied. Glucose and caffeine stimulated synthase phosphatase activity in a synergistic manner. With 0.5 mM caffeine the A0.5 for glucose was 11 mM (from 27 mM), whereas in the presence of 30 mM glucose the A0.5 for caffeine was 0.06 mM (from 0.7 mM). At 10 mM glucose the A0.5 for caffeine was 0.1 mM. Glucose stimulation remained non-cooperative, unaffected by the presence of caffeine, whereas the cooperative stimulation of caffeine was unaffected by glucose. Some slight stimulation of synthase activity was observed with caffeine and with glucose over a wide concentration range. However, they did not act synergistically to influence the measurement of synthase activity. Glucose-6-phosphate, which also stimulates synthase phosphatase activity, acted independently, not synergistically with caffeine. All the methylxanthines were tested as potential second effectors in an effort to discover the essential structural elements of the agent. All dimethylxanthines, 3- and 7-methylxanthine and 1-methyl-3-isobutylxanthine enhanced glucose stimulation but none of them alone was stimulatory. Judged from the half-maximal concentrations, in the presence of 10 mM glucose, caffeine was the most potent second effector by a significant margin. The maximum velocity was also greatest with caffeine, whereas that with other methylxanthines was generally lower, and varied. 1-Methylxanthine with increased concentration was slightly inhibitory even in the presence of 10 mM glucose. Xanthine (0.5 mM), itself, strongly inhibited synthase phosphatase activity, an effect not influenced by glucose. Xanthine did not influence the measurement of synthase or phosphorylase phosphatase activity with or without glucose. In general, conditions of methylxanthine-enhanced, glucose stimulation of synthase phosphatase and phosphorylase phosphatase activities differed markedly, confirming that separate, distinct mechanisms are involved.

UI	MeSH Term	Description	Entries
D008099	Liver	A large lobed glandular organ in the abdomen of vertebrates that is responsible for detoxification, metabolism, synthesis and storage of various substances.	Livers
D008297	Male		Males
D010749	Phosphoprotein Phosphatases	A group of enzymes removing the SERINE- or THREONINE-bound phosphate groups from a wide range of phosphoproteins, including a number of enzymes which have been phosphorylated under the action of a kinase. (Enzyme Nomenclature, 1992)	Phosphoprotein Phosphatase,Phosphoprotein Phosphohydrolase,Protein Phosphatase,Protein Phosphatases,Casein Phosphatase,Ecto-Phosphoprotein Phosphatase,Nuclear Protein Phosphatase,Phosphohistone Phosphatase,Phosphoprotein Phosphatase-2C,Phosphoseryl-Protein Phosphatase,Protein Phosphatase C,Protein Phosphatase C-I,Protein Phosphatase C-II,Protein Phosphatase H-II,Protein-Serine-Threonine Phosphatase,Protein-Threonine Phosphatase,Serine-Threonine Phosphatase,Threonine Phosphatase,Ecto Phosphoprotein Phosphatase,Phosphatase C, Protein,Phosphatase C-I, Protein,Phosphatase C-II, Protein,Phosphatase H-II, Protein,Phosphatase, Casein,Phosphatase, Ecto-Phosphoprotein,Phosphatase, Nuclear Protein,Phosphatase, Phosphohistone,Phosphatase, Phosphoprotein,Phosphatase, Phosphoseryl-Protein,Phosphatase, Protein,Phosphatase, Protein-Serine-Threonine,Phosphatase, Protein-Threonine,Phosphatase, Serine-Threonine,Phosphatase, Threonine,Phosphatase-2C, Phosphoprotein,Phosphatases, Phosphoprotein,Phosphatases, Protein,Phosphohydrolase, Phosphoprotein,Phosphoprotein Phosphatase 2C,Phosphoseryl Protein Phosphatase,Protein Phosphatase C I,Protein Phosphatase C II,Protein Phosphatase H II,Protein Phosphatase, Nuclear,Protein Serine Threonine Phosphatase,Protein Threonine Phosphatase,Serine Threonine Phosphatase
D002110	Caffeine	A methylxanthine naturally occurring in some beverages and also used as a pharmacological agent. Caffeine's most notable pharmacological effect is as a central nervous system stimulant, increasing alertness and producing agitation. It also relaxes SMOOTH MUSCLE, stimulates CARDIAC MUSCLE, stimulates DIURESIS, and appears to be useful in the treatment of some types of headache. Several cellular actions of caffeine have been observed, but it is not entirely clear how each contributes to its pharmacological profile. Among the most important are inhibition of cyclic nucleotide PHOSPHODIESTERASES, antagonism of ADENOSINE RECEPTORS, and modulation of intracellular calcium handling.	1,3,7-Trimethylxanthine,Caffedrine,Coffeinum N,Coffeinum Purrum,Dexitac,Durvitan,No Doz,Percoffedrinol N,Percutaféine,Quick-Pep,Vivarin,Quick Pep,QuickPep
D004347	Drug Interactions	The action of a drug that may affect the activity, metabolism, or toxicity of another drug.	Drug Interaction,Interaction, Drug,Interactions, Drug
D005947	Glucose	A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement.	Dextrose,Anhydrous Dextrose,D-Glucose,Glucose Monohydrate,Glucose, (DL)-Isomer,Glucose, (alpha-D)-Isomer,Glucose, (beta-D)-Isomer,D Glucose,Dextrose, Anhydrous,Monohydrate, Glucose
D005958	Glucosephosphates
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D013329	Structure-Activity Relationship	The relationship between the chemical structure of a compound and its biological or pharmacological activity. Compounds are often classed together because they have structural characteristics in common including shape, size, stereochemical arrangement, and distribution of functional groups.	Relationship, Structure-Activity,Relationships, Structure-Activity,Structure Activity Relationship,Structure-Activity Relationships
D013805	Theobromine	3,7-Dimethylxanthine. The principle alkaloid in Theobroma cacao (the cacao bean) and other plants. A xanthine alkaloid that is used as a bronchodilator and as a vasodilator. It has a weaker diuretic activity than THEOPHYLLINE and is also a less powerful stimulant of smooth muscle. It has practically no stimulant effect on the central nervous system. It was formerly used as a diuretic and in the treatment of angina pectoris and hypertension. (From Martindale, The Extra Pharmacopoeia, 30th ed, pp1318-9)