Biomaterial Database

Properties of ATPase activity in coupling factor from Chromatium strain D chromatophores. 1977

A Gepshtein, and C Carmeli

Coupling factor extracted from chromatophores of the photosynthetic bacteria Chromatium strain D was partially purified. The enzyme catalyzed ATPase activity in the presence of Ca2+ and Mg2+ ions. Higher Vapp values were obtained when the activity was measured as a function of the divalent cation-ATP complex rather than as a function of either the divalent cation or ATP because the free components competitively inhibited the activity in the presence of the cation-ATP complex. The Km values were lower than or equal to the Ki values for free ATP indicating that the cation-ATP complex is bound tighter than the free ATP to the enzyme. Based on these results a possible mode of binding of substrate to the active site of the enzyme was suggested. A comparative study indicated no changes in the temperature dependance of ATPase activity when the enzyme was solubilized. However, possible conformation changes could have caused a decrease in the Km values for the (Ca-ATP)2- and (Mg-ATP)2- and in the Ki for free Mg2+ ions and ATP. The Ki for free Ca2+ ions increased on solubilization of the coupling factor. ATPase activity was inhibited by dicyclohexylcarbodiimide both in the soluble and in the membrane-bound coupling factor.

UI	MeSH Term	Description	Entries
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D008274	Magnesium	A metallic element that has the atomic symbol Mg, atomic number 12, and atomic weight 24.31. It is important for the activity of many enzymes, especially those involved in OXIDATIVE PHOSPHORYLATION.
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
D002844	Chromatium	A genus of gram-negative, ovoid to rod-shaped bacteria that is phototrophic. All species use ammonia as a nitrogen source. Some strains are found only in sulfide-containing freshwater habitats exposed to light while others may occur in marine, estuarine, and freshwater environments.
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
D000251	Adenosine Triphosphatases	A group of enzymes which catalyze the hydrolysis of ATP. The hydrolysis reaction is usually coupled with another function such as transporting Ca(2+) across a membrane. These enzymes may be dependent on Ca(2+), Mg(2+), anions, H+, or DNA.	ATPases,Adenosinetriphosphatase,ATPase,ATPase, DNA-Dependent,Adenosine Triphosphatase,DNA-Dependent ATPase,DNA-Dependent Adenosinetriphosphatases,ATPase, DNA Dependent,Adenosinetriphosphatases, DNA-Dependent,DNA Dependent ATPase,DNA Dependent Adenosinetriphosphatases,Triphosphatase, Adenosine
D001426	Bacterial Proteins	Proteins found in any species of bacterium.	Bacterial Gene Products,Bacterial Gene Proteins,Gene Products, Bacterial,Bacterial Gene Product,Bacterial Gene Protein,Bacterial Protein,Gene Product, Bacterial,Gene Protein, Bacterial,Gene Proteins, Bacterial,Protein, Bacterial,Proteins, Bacterial
D001429	Bacteriochlorophylls	Pyrrole containing pigments found in photosynthetic bacteria.	Bacteriochlorophyll
D013696	Temperature	The property of objects that determines the direction of heat flow when they are placed in direct thermal contact. The temperature is the energy of microscopic motions (vibrational and translational) of the particles of atoms.	Temperatures
D020130	Bacterial Chromatophores	Organelles of phototrophic bacteria which contain photosynthetic pigments and which are formed from an invagination of the cytoplasmic membrane.	Chromatophores, Bacterial,Bacterial Chromatophore,Chromatophore, Bacterial