Biomaterial Database

Mitochondrial GTP-AMP phosphotransferase. 2. Kinetic and equilibrium dialysis studies. 1979

A G Tomasselli, and L H Noda

Kinetic and equilibrium dialysis substrate binding studies have been done to investigate the properties of mitochondrial GTP-AMP phosphotransferase. The results show that the enzyme has a specific requirement for divalent metal ions, namely Mg2+, Mn2+ or Ca2+ (Ca2+ is active only in the forward direction, the direction of formation of ADP). The reaction rate depends upon the ratio [Mg2+]:[substrate] rather than on the metal ion concentration alone. The enzymatic activity is influenced by NaCl (or KCl) and optimum pH occurs at 11.5 and 9.5 for guanosine and inosine nucleotides respectively. Examination of binding of substrates to the enzyme showed that there is one binding site (GTP site) for MgGTP, GTP, MgGDP or GDP per molecule of enzyme, with dissociation constants of 4.5, 4.4, 3.0, 2.2 micron respectively and one binding site (AMP site) for AMP, ADP or ATP per molecule of enzyme with dissociation constants of 20.9, 33.4 and 33.4 microns respectively. Since, within the limitations of equilibrium dialysis used in the present studies, AMP binding to one site of the enzyme could be detected only when GDP or GTP is present, the mechanism of the forward reaction may be assumed to be nearly ordered. For the reverse reaction there is no requirement of order of binding of the two nucleotides and so the mechanism of reaction may be assumed to be random.

UI	MeSH Term	Description	Entries
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D008929	Mitochondria, Heart	The mitochondria of the myocardium.	Heart Mitochondria,Myocardial Mitochondria,Mitochondrion, Heart,Heart Mitochondrion,Mitochondria, Myocardial
D009703	Nucleoside-Phosphate Kinase	An enzyme that catalyzes reversible reactions of a nucleoside triphosphate, e.g., ATP, with a nucleoside monophosphate, e.g., UMP, to form ADP and UDP. Many nucleoside monophosphates can act as acceptor while many ribo- and deoxyribonucleoside triphosphates can act as donor. EC 2.7.4.4.	Nucleoside Monophosphate Kinases,Kinase, Nucleoside-Phosphate,Kinases, Nucleoside Monophosphate,Monophosphate Kinases, Nucleoside,Nucleoside Phosphate Kinase
D009994	Osmolar Concentration	The concentration of osmotically active particles in solution expressed in terms of osmoles of solute per liter of solution. Osmolality is expressed in terms of osmoles of solute per kilogram of solvent.	Ionic Strength,Osmolality,Osmolarity,Concentration, Osmolar,Concentrations, Osmolar,Ionic Strengths,Osmolalities,Osmolar Concentrations,Osmolarities,Strength, Ionic,Strengths, Ionic
D010770	Phosphotransferases	A rather large group of enzymes comprising not only those transferring phosphate but also diphosphate, nucleotidyl residues, and others. These have also been subdivided according to the acceptor group. (From Enzyme Nomenclature, 1992) EC 2.7.	Kinases,Phosphotransferase,Phosphotransferases, ATP,Transphosphorylase,Transphosphorylases,Kinase,ATP Phosphotransferases
D002413	Cations, Divalent	Positively charged atoms, radicals or groups of atoms with a valence of plus 2, which travel to the cathode or negative pole during electrolysis.	Divalent Cations
D002417	Cattle	Domesticated bovine animals of the genus Bos, usually kept on a farm or ranch and used for the production of meat or dairy products or for heavy labor.	Beef Cow,Bos grunniens,Bos indicus,Bos indicus Cattle,Bos taurus,Cow,Cow, Domestic,Dairy Cow,Holstein Cow,Indicine Cattle,Taurine Cattle,Taurus Cattle,Yak,Zebu,Beef Cows,Bos indicus Cattles,Cattle, Bos indicus,Cattle, Indicine,Cattle, Taurine,Cattle, Taurus,Cattles, Bos indicus,Cattles, Indicine,Cattles, Taurine,Cattles, Taurus,Cow, Beef,Cow, Dairy,Cow, Holstein,Cows,Dairy Cows,Domestic Cow,Domestic Cows,Indicine Cattles,Taurine Cattles,Taurus Cattles,Yaks,Zebus
D003956	Dialysis	A process of selective diffusion through a membrane. It is usually used to separate low-molecular-weight solutes which diffuse through the membrane from the colloidal and high-molecular-weight solutes which do not. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)	Dialyses
D006160	Guanosine Triphosphate	Guanosine 5'-(tetrahydrogen triphosphate). A guanine nucleotide containing three phosphate groups esterified to the sugar moiety.	GTP,Triphosphate, Guanosine
D000249	Adenosine Monophosphate	Adenine nucleotide containing one phosphate group esterified to the sugar moiety in the 2'-, 3'-, or 5'-position.	AMP,Adenylic Acid,2'-AMP,2'-Adenosine Monophosphate,2'-Adenylic Acid,5'-Adenylic Acid,Adenosine 2'-Phosphate,Adenosine 3'-Phosphate,Adenosine 5'-Phosphate,Adenosine Phosphate Dipotassium,Adenosine Phosphate Disodium,Phosphaden,2' Adenosine Monophosphate,2' Adenylic Acid,5' Adenylic Acid,5'-Phosphate, Adenosine,Acid, 2'-Adenylic,Acid, 5'-Adenylic,Adenosine 2' Phosphate,Adenosine 3' Phosphate,Adenosine 5' Phosphate,Dipotassium, Adenosine Phosphate,Disodium, Adenosine Phosphate,Monophosphate, 2'-Adenosine,Phosphate Dipotassium, Adenosine,Phosphate Disodium, Adenosine