Biomaterial Database

Phosphoenolpyruvate carboxykinase in mouse pancreatic islets. ATP-induced changes in sensitivity to Mn2+ activation. 1984

C J Hedeskov, and K Capito, and P Thams

The presence of high phosphoenolpyruvate carboxykinase (EC 4.1.1.32) activity in mouse islet cytosol has been demonstrated. The enzyme was activated by Mn2+ with a Ka of 100 X 10(-6) mol/l. The mean total activity of the Mn2+-stimulated phosphoenolpyruvate carboxykinase in islet cytosol estimated at 22 degrees C with saturating concentrations of the substrates oxaloacetate and ITP was 146 pmol/min per micrograms DNA. Km was calculated to be 6 X 10(-6) mol/l for oxaloacetate and 140 X 10(-6) mol/l for ITP. The islet phosphoenolpyruvate carboxykinase activity was not increased after starvation of the animals for 48 h. Preincubation of the cytosol at 4 degrees C with Fe2+, quinolinate, ATP, Pi, glucose 6-phosphate, fructose 1,6-bisphosphate, NAD+, NADH, oxaloacetate, ITP, cyclic AMP and Ca2+ had no effect on the enzyme activity. However, preincubation of the cytosol at 37 degrees C with ATP-Mg inhibited the Mn2+-stimulated phosphoenolpyruvate carboxykinase activity progressively with time and in a concentration-dependent manner. A similar but weaker inhibitory effect was observed with p[NH]ppA, whereas p[CH2]ppA, ADP, AMP, adenosine and Pi had no effect. It is tentatively suggested that ATP and p[NH]ppA either by adenylation or otherwise affect the interaction between islet phosphoenolpyruvate carboxykinase and the recently discovered Mr = 29000 protein modulator of the enzyme in such a way - perhaps by causing a dissociation between them - that phosphoenolpyruvate carboxykinase loses its sensitivity to Mn2+ activation.

UI	MeSH Term	Description	Entries
D007515	Islets of Langerhans	Irregular microscopic structures consisting of cords of endocrine cells that are scattered throughout the PANCREAS among the exocrine acini. Each islet is surrounded by connective tissue fibers and penetrated by a network of capillaries. There are four major cell types. The most abundant beta cells (50-80%) secrete INSULIN. Alpha cells (5-20%) secrete GLUCAGON. PP cells (10-35%) secrete PANCREATIC POLYPEPTIDE. Delta cells (~5%) secrete SOMATOSTATIN.	Islands of Langerhans,Islet Cells,Nesidioblasts,Pancreas, Endocrine,Pancreatic Islets,Cell, Islet,Cells, Islet,Endocrine Pancreas,Islet Cell,Islet, Pancreatic,Islets, Pancreatic,Langerhans Islands,Langerhans Islets,Nesidioblast,Pancreatic Islet
D008297	Male		Males
D008345	Manganese	A trace element with atomic symbol Mn, atomic number 25, and atomic weight 54.94. It is concentrated in cell mitochondria, mostly in the pituitary gland, liver, pancreas, kidney, and bone, influences the synthesis of mucopolysaccharides, stimulates hepatic synthesis of cholesterol and fatty acids, and is a cofactor in many enzymes, including arginase and alkaline phosphatase in the liver. (From AMA Drug Evaluations Annual 1992, p2035)
D010729	Phosphoenolpyruvate Carboxykinase (GTP)	An enzyme of the lyase class that catalyzes the conversion of GTP and oxaloacetate to GDP, phosphoenolpyruvate, and carbon dioxide. This reaction is part of gluconeogenesis in the liver. The enzyme occurs in both the mitochondria and cytosol of mammalian liver. (From Dorland, 27th ed) EC 4.1.1.32.	GTP-Dependent Phosphoenolpyruvate Carboxykinase,Carboxykinase, GTP-Dependent Phosphoenolpyruvate,GTP Dependent Phosphoenolpyruvate Carboxykinase,Phosphoenolpyruvate Carboxykinase, GTP-Dependent
D002118	Calcium	A basic element found in nearly all tissues. It is a member of the alkaline earth family of metals with the atomic symbol Ca, atomic number 20, and atomic weight 40. Calcium is the most abundant mineral in the body and combines with phosphorus to form calcium phosphate in the bones and teeth. It is essential for the normal functioning of nerves and muscles and plays a role in blood coagulation (as factor IV) and in many enzymatic processes.	Coagulation Factor IV,Factor IV,Blood Coagulation Factor IV,Calcium-40,Calcium 40,Factor IV, Coagulation
D003600	Cytosol	Intracellular fluid from the cytoplasm after removal of ORGANELLES and other insoluble cytoplasmic components.	Cytosols
D004789	Enzyme Activation	Conversion of an inactive form of an enzyme to one possessing metabolic activity. It includes 1, activation by ions (activators); 2, activation by cofactors (coenzymes); and 3, conversion of an enzyme precursor (proenzyme or zymogen) to an active enzyme.	Activation, Enzyme,Activations, Enzyme,Enzyme Activations
D005296	Ferrous Compounds	Inorganic or organic compounds that contain divalent iron.	Compounds, Ferrous
D006019	Glycolysis	A metabolic process that converts GLUCOSE into two molecules of PYRUVIC ACID through a series of enzymatic reactions. Energy generated by this process is conserved in two molecules of ATP. Glycolysis is the universal catabolic pathway for glucose, free glucose, or glucose derived from complex CARBOHYDRATES, such as GLYCOGEN and STARCH.	Embden-Meyerhof Pathway,Embden-Meyerhof-Parnas Pathway,Embden Meyerhof Parnas Pathway,Embden Meyerhof Pathway,Embden-Meyerhof Pathways,Pathway, Embden-Meyerhof,Pathway, Embden-Meyerhof-Parnas,Pathways, Embden-Meyerhof
D000255	Adenosine Triphosphate	An adenine nucleotide containing three phosphate groups esterified to the sugar moiety. In addition to its crucial roles in metabolism adenosine triphosphate is a neurotransmitter.	ATP,Adenosine Triphosphate, Calcium Salt,Adenosine Triphosphate, Chromium Salt,Adenosine Triphosphate, Magnesium Salt,Adenosine Triphosphate, Manganese Salt,Adenylpyrophosphate,CaATP,CrATP,Manganese Adenosine Triphosphate,MgATP,MnATP,ATP-MgCl2,Adenosine Triphosphate, Chromium Ammonium Salt,Adenosine Triphosphate, Magnesium Chloride,Atriphos,Chromium Adenosine Triphosphate,Cr(H2O)4 ATP,Magnesium Adenosine Triphosphate,Striadyne,ATP MgCl2