Journal ArticleDOI
A simple analysis of the "phosphocreatine shuttle"
TLDR
Experimental results demonstrating the transport aspects of the CK reaction emphasize only one feature of a more general notion of facilitated diffusion by near-equilibrium metabolic reactions and do not per se establish the existence of any physical or functional compartmentation of ATP, ADP, PCr, or creatine.Abstract:
The diffusive mobility of solutes chemically connected by reversible reactions in cells is analyzed as a problem of facilitated diffusion. By this term we mean that the diffusive flux of any substance, X, which is in one metabolic pathway, is effectively increased when it participates in a second and equilibrium reaction with another substance Y because the total flux of X in the pathway is the sum of the fluxes of X and Y. This notion is generalized and is seen to include the familiar enhanced intracellular diffusion of oxygen by oxymyoglobin. In this framework the function of creatine kinase (CK) is seen to have two aspects: 1) phosphocreatine (PCr) via the CK reaction buffers the cellular ATP and ADP concentrations and 2) transport of high-energy phosphates is predominantly in the chemical form of PCr. This predominance of PCr is a consequence of the maintained ATP, ADP, and total creatine levels and of the apparent equilibrium constant of the reaction. Thus experimental results demonstrating the transport aspects of the CK reaction emphasize only one feature of a more general notion of facilitated diffusion by near-equilibrium metabolic reactions and do not per se establish the existence of any physical or functional compartmentation of ATP, ADP, PCr, or creatine. PCr can be a large source for increasing inorganic phosphate levels during contractile activity, possibly as a metabolic regulator. Neither the transport nor buffer aspects can be quantitatively important in cells with small distances between ATP-utilizing and ATP-generating sites, such as is the case with cardiac myofibrils and mitochondria.read more
Citations
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myocytesand tension development in isolated single Effects of acute creatine kinase inhibition on
Michael C. Hogan,Casey A. Kindig,Richard A. Howlett,Creed M. Stary,Brandon Walsh,Stephen J. Bailey,Anni Vanhatalo,Daryl P. Wilkerson,Fred J. DiMenna,Andrew M. Jones,Leonardo Nogueira,Juan M. Murias,Matthew D. Spencer,Darren S. DeLorey,Brendon J. Gurd,Mina John +15 more
Book ChapterDOI
Creatine Kinase and Mechanical Properties of Rat Ventricular Muscle
TL;DR: The MM-creatine kinase has also been identified as a constituant of the M band in the sarcomere of skeletal and heart muscle and is able to rephosphoryl ate MgADP produced during activation of the actomyosin ATPase.
References
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Journal ArticleDOI
The number and distribution of capillaries in muscles with calculations of the oxygen pressure head necessary for supplying the tissue.
Journal ArticleDOI
Mapping of metabolites in whole animals by 31P NMR using surface coils.
TL;DR: The metabolic state of skeletal muscle and brain within intact rats is monitored using high resolution phosphorus nuclear magnetic resonance, indicating the diagnostic possibilities of the method.
Journal ArticleDOI
Cytosolic phosphorylation potential.
TL;DR: Agreement between two highly active enzyme systems in the same compartment is taken as evidence of the existence of near-equilibrium in both these systems and suggests that free cytosolic [sigma ADP] is probably 20-fold lower than measured cell ADP content in mitochondrial-containing tissues.
Journal ArticleDOI
Transport of energy in muscle: the phosphorylcreatine shuttle
Samuel P. Bessman,Paul J. Geiger +1 more
TL;DR: It was proposed in 1951 that contracting muscle fibers liberate creatine, which acts to produce an acceptor effect--later called respiratory control--on the muscle mitochondria, which established a molecular basis for a phosphorylcreatine-creatine shuttle for energy transport in heart and skeletal muscle.
Journal ArticleDOI
Effects of pH and free Mg2+ on the Keq of the creatine kinase reaction and other phosphate hydrolyses and phosphate transfer reactions.
J W Lawson,R L Veech +1 more
TL;DR: The observed equilibrium constants (Kobs) of the creatine kinase, myokinase, glucose-6-phosphatase, and fructose-1,6-diph phosphatase reactions have been determined at 38 degrees C, pH 7.0, ionic strength 0.25, and varying free magnesium concentrations.
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Transport of energy in muscle: the phosphorylcreatine shuttle
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