Regulating ATP turnover rates over broad dynamic work ranges in skeletal muscles

rates over broad dynamic work ranges in skeletal muscles. J. Appl. Physiol. 73(5): 1697-1703, 1992.-It has long been appreciated that rates of ATP utilization and production need to be extremely closely balanced. To put it in molecular rather than molar terms, in human muscle engaged in a 15-min work protocol, ~3.3 X 102 ’ ATP/g are used and resynthesized at- 100 times the resting cycling rates before fatigue, during which time only a 20-25 % decrease in the ATP pool is sustained. Analysis of how such re-markable regulatory precision is achieved suggests that in resting muscle myosin behaves as a latent catalyst whose full catalytic potential 1) is real-ized with the arrival of an activator signal (Ca2’) and 2) is tempered with reaction products; such proactive control, initiated at ATP utilization, sets the required flux through ATP-producing pathways. For any given enzyme step in ATP-producing pathways, reaction velocity (v) becomes the inde-pendent parameter, with substrate concentration ([S], the dependent pa-rameter) being adjusted accordingly. Because the dynamic range for mus