Rate equation for creatine kinase predicts the in vivo reaction velocity: /sup 31/P NMR surface coil studies in brain, heart, and skeletal muscle of the living rat
Brain, heart, and skeletal muscle contain four different creatine kinase isozymes and various concentrations of substrates for the creatine kinase reaction. To identify if the velocity of the creatine kinase reaction under cellular conditions is regulated by enzyme activity and substrate concentrations as predicted by the rate equation, the authors used /sup 31/P NMR and spectrophotometric techniques to measure reaction velocity, enzyme content, isozyme distribution, and concentrations of substrates in brain, heart, and skeletal muscle of living rat under basal or resting conditions. The total tissue activity of creatine kinase in the direction of MgATP synthesis provided an estimate for V/sub max/ and exceeded the NMR-determined in vivo reaction velocities by an order of magnitude. The isozyme composition varied among the three tissues: >99% BB for brain; 14% MB, 61% MM, and 25% mitochondrial for heart; and 98% MM and 2% mitochondrial for skeletal muscle. The NMR-determined reaction velocities agreed with predicted values from the creatine kinase rate equation. The concentrations of free creatine and cytosolic MgADP, being less than or equal to the dissociation constants for each isozyme, were dominant terms in the creatine kinase rate equation for predicting the in vivo reaction velocity. Thus, they observed that the velocity of the creatine kinase reaction is regulated by total tissue enzyme activity and by the concentrations of creatine and MgADP in a manner that is independent of isozyme distribution.
- Research Organization:
- Brigham and Women's Hospital, Boston, MA
- OSTI ID:
- 5599189
- Journal Information:
- Biochemistry; (United States), Vol. 26:19
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
59 BASIC BIOLOGICAL SCIENCES
BRAIN
NUCLEAR MAGNETIC RESONANCE
HEART
MUSCLES
PHOSPHOTRANSFERASES
BIOCHEMICAL REACTION KINETICS
CREATINE
IN VIVO
ISOENZYMES
PHOSPHORUS 31
RATS
SUBSTRATES
AMINO ACIDS
ANIMALS
BODY
CARBOXYLIC ACIDS
CARDIOVASCULAR SYSTEM
CENTRAL NERVOUS SYSTEM
ENZYMES
ISOTOPES
KINETICS
LIGHT NUCLEI
MAGNETIC RESONANCE
MAMMALS
NERVOUS SYSTEM
NUCLEI
ODD-EVEN NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANS
PHOSPHORUS ISOTOPES
PHOSPHORUS-GROUP TRANSFERASES
REACTION KINETICS
RESONANCE
RODENTS
STABLE ISOTOPES
TRANSFERASES
VERTEBRATES
550601* - Medicine- Unsealed Radionuclides in Diagnostics
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