CREATINE-KINASE EQUILIBRATION FOLLOWS SOLUTION THERMODYNAMICS IN SKELETAL-MUSCLE - P-31 NMR-STUDIES USING CREATINE ANALOGS

被引:49
作者
WISEMAN, RW
KUSHMERICK, MJ
机构
[1] UNIV WASHINGTON,MED CTR,DEPT PHYSIOL & BIOPHYS,SEATTLE,WA 98195
[2] UNIV WASHINGTON,MED CTR,CTR BIOENGN,SEATTLE,WA 98195
关键词
D O I
10.1074/jbc.270.21.12428
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
The hypothesis tested was whether creatine kinase (CK) equilibrates with its substrates and products in the cytosol as if in solution. We used the creatine analogs cyclocreatine (cCr) or beta-guanidopropionate (beta GPA) to test if mass action ratios (Gamma) for CK in muscle could be predicted from combined equilibrium constants (K-comb) measured in solutions mimicking the intracellular environment. Mice were fed cCr or beta GPA and their muscles assayed for substrates and products of the CK reaction by P-31 NMR spectroscopy and high performance liquid chromatography. After three weeks of feeding, Gamma was indistinguishable from K-comb in cCr-treated muscles demonstrating both PCr/Cr and phospho-analog/analog must have equilibrated with a constant and uniform cellular ATP/ADP ratio. In beta GPA-treated muscles, Gamma was smaller than K-comb due to a higher content of muscle beta GPA. Feeding beta GPA for 9-12 weeks resulted in a closer agreement between K-comb and Gamma, suggesting ATP/ADP ratios are not uniform within the muscle perhaps due to transient metabolic stress in some cells. From this analysis it follows that calculation of free ADP from the CII: equilibrium for a heterogeneous population of cells with respect to total Cr and ATP content is correct only if chemical potentials of these cells are uniform.
引用
收藏
页码:12428 / 12438
页数:11
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