Effect of pH and inorganic phosphate on creatine kinase inactivation: an in vitro 31P NMR saturation-transfer study.
The pseudo-first-order rate constant of rabbit muscle creatine kinase (CK), in the direction of ATP synthesis (kf), was determined by saturation-transfer 31P NMR. When pH was varied between 6.0 and 7.4, kf increased linearly at both 20 degrees C and 37 degrees c. The corresponding flux is very small between pH 6.0 and 6.5, in contrast to previous studies. Up to 50 h exposure of the CK enzyme to high concentrations of inorganic phosphate (Pi), a known inhibitor in certain situations, had negligible effect on enzymatic flux in the physiological pH range. Thus under in vivo conditions, such as in stroke, where pH falls as low as 6.2 and Pi rises to high levels, the rate of the CK reaction may be severely reduced due to pH but not due to high Pi concentrations.
Williams
G D
GD
Department of Radiology, Pennsylvania State University College of Medicine, Milton S. Hershey Medical Center, Hershey 17033.
Enders
B
B
Smith
M B
MB
D000255:Adenosine Triphosphate / Q000096:biosynthesis; D000818:Animals; D003402:Creatine Kinase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D009132:Muscles / Q000201:enzymology*; D010710:Phosphates / Q000378:metabolism / Q000494:pharmacology*; D011817:Rabbits
D010710:Phosphates; D000255:Adenosine Triphosphate; D003402:Creatine Kinase