Activity of creatine kinase in a contracting mammalian muscle of uniform fiber type.
Biophys J
; 67(5): 1912-24, 1994 Nov.
Article
en En
| MEDLINE
| ID: mdl-7858128
ABSTRACT
We investigated whether the creatine kinase-catalyzed phosphate exchange between PCr and gamma ATP in vivo equilibrated with cellular substrates and products as predicted by in vitro kinetic properties of the enzyme, or was a function of ATPase activity as predicted by obligatory "creatine phosphate shuttle" concepts. A transient NMR spin-transfer method was developed, tested, and applied to resting and stimulated ex vivo muscle, the soleus, which is a cellularly homogeneous slow-twitch mammalian muscle, to measure creatine kinase kinetics. The forward and reverse unidirectional CK fluxes were equal, being 1.6 mM.s-1 in unstimulated muscle at 22 degrees C, and 2.7 mM.s-1 at 30 degrees C. The CK fluxes did not differ during steady-state stimulation conditions giving a 10-fold range of ATPase rates in which the ATP/PCr ratio increased from approximately 0.3 to 1.6. The observed kinetic behavior of CK activity in the muscle was that expected from the enzyme in vitro in a homogeneous solution only if account was taken of inhibition by an anion-stabilized quaternary dead-end enzyme complex E.Cr.MgADP.anion. The CK fluxes in soleus were not a function of ATPase activity as predicted by obligatory phosphocreatine shuttle models for cellular energetics.
Texto completo:
1
Banco de datos:
MEDLINE
Asunto principal:
Músculo Esquelético
/
Creatina Quinasa
Tipo de estudio:
Prognostic_studies
Límite:
Animals
Idioma:
En
Año:
1994
Tipo del documento:
Article