Smith M B, Briggs R W, Shoubridge E A, Hayes D J, Radda G K
Biochim Biophys Acta. 1985 Jul 30;846(1):174-8. doi: 10.1016/0167-4889(85)90123-5.
The maximum activity of creatine kinase in vitro is similar in the pectoralis major muscle of the chicken and the duck. However, the flux (phosphocreatine to ATP) as measured by 31P saturation transfer NMR in vivo is almost 2-fold higher in the duck. This apparent discrepancy can be accounted for by the differences in the cytosolic free ADP concentrations in resting muscle.
