title: [ATP-phosphocreatine metabolism catalyzed by creatine kinase. Comparison of saturation transfer (NMR) and isotope labeling technics].
abstract: Unidirectional fluxes from ATP to phosphocreatine (PCr) catalyzed by MM-isoenzyme of creatine kinase (CK) were measured by using 31P-NMR saturation transfer technique and by means of radioactively labeled [gamma-32P]ATP. At 30-37 degrees C and pH 7.4 in a wide range of [PCr]/[creatine] ([PCr]/[Cr]) ratios (0.2 to 3.0) both of these methods gave similar results, thus showing that magnetization (saturation) transfer allows to determine fluxes close to real ones under "physiological" conditions. However, at [PCr]/[Cr] ratio higher than 5 ([ADP] less than 30 microM) or at decreased temperatures (7-15 degrees C, [PCr]/[Cr] approximately 1) fluxes determined by saturation transfer substantially exceeded those measured with the radioactive label. These data imply that under "physiological" conditions phosphoryl group transfer is actually rate-determining step of the CK reaction. On the contrary, at high [PCr]/[Cr] values or at low temperature the control step could be shifted from the phosphoryl group transfer or distributed among other steps of the reaction.
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D002384:Catalysis; D003402:Creatine Kinase / Q000378:metabolism*; D066298:In Vitro Techniques; D007553:Isotope Labeling; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D009132:Muscles / Q000201:enzymology / Q000378:metabolism; D010725:Phosphocreatine / Q000378:metabolism*; D051381:Rats
chemical_list: D010725:Phosphocreatine; D000255:Adenosine Triphosphate; D003402:Creatine Kinase
vernacular_title: Izuchenie obmena ATP-fosfokreatin, kataliziruemogo kreatinkinazoĭ. Sravnenie tekhniki perenosa nasyshcheniia (IaMR) i metoda izotopnoĭ metki.