Kinetic, thermodynamic, and developmental consequences of deleting creatine kinase isoenzymes from the heart. Reaction kinetics of the creatine kinase isoenzymes in the intact heart.
Creatine kinase (CK) exists as a family of isoenzymes in excitable tissue. We studied isolated perfused hearts from mice lacking genes for either the main muscle isoform of CK (M-CK) or both M-CK and the main mitochondrial isoform (Mt-CK) to determine 1) the biological significance of CK isoenzyme shifts, 2) the necessity of maintaining a high CK reaction rate, and 3) the role of CK isoenzymes in establishing the thermodynamics of ATP hydrolysis. (31)P NMR was used to measure [ATP], [PCr], [P(i)], [ADP], pH, as well as the unidirectional reaction rate of PCr--> [gamma-P]ATP. Developmental changes in the main fetal isoform of CK (BB-CK) were unaffected by loss of other CK isoenzymes. In hearts lacking both M- and Mt-CK, the rate of ATP synthesis from PCr was only 9% of the rate of ATP synthesis from oxidative phosphorylation demonstrating a lack of any high energy phosphate shuttle. We also found that the intrinsic activities of the BB-CK and the MM-CK isoenzymes were equivalent. Finally, combined loss of M- and Mt-CK (but not loss of only M-CK) prevented the amount of free energy released from ATP hydrolysis from increasing when pyruvate was provided as a substrate for oxidative phosphorylation.
Saupe
K W
KW
Cardiac Muscle Research Laboratory, Boston University School of Medicine, Boston, Massachusetts 02118, USA.
Spindler
M
M
Hopkins
J C
JC
Shen
W
W
Ingwall
J S
JS
D000255:Adenosine Triphosphate / Q000378:metabolism; D000367:Age Factors; D000818:Animals; D000831:Animals, Newborn; D002851:Chromatography, High Pressure Liquid; D003402:Creatine Kinase / Q000737:chemistry* / Q000235:genetics* / Q000502:physiology; D005947:Glucose / Q000378:metabolism; D006321:Heart / Q000196:embryology*; D006863:Hydrogen-Ion Concentration; D007527:Isoenzymes / Q000737:chemistry / Q000235:genetics / Q000502:physiology; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D051379:Mice; D008817:Mice, Mutant Strains; D009206:Myocardium / Q000201:enzymology*; D010100:Oxygen / Q000378:metabolism; D010477:Perfusion; D019289:Pyruvic Acid / Q000378:metabolism; D013816:Thermodynamics; D013997:Time Factors
D007527:Isoenzymes; D019289:Pyruvic Acid; D000255:Adenosine Triphosphate; D003402:Creatine Kinase; D005947:Glucose; D010100:Oxygen