ATP turnover

Funatsu T, Flarada Y, Tokunaga M, Saito K and Yanagida T 1995 Imaging of single fluorescent molecules and individual ATP turnovers by single myosin molecules in aqueous solution Nature 374 555-9... 

Fnnatsn, T, Harada, Y, Toknnaga, M., et al., 1995. Imaging of single fluorescent molecnles and individual ATP turnovers by single myosin mole-cnles in aqueous solution. 374 555-559. 

In dass 3, the rate of metabolite production from a single substrate may be limited by the rate of ATP turnover. Provision of ready made precursors can increase both the metabolite yield (final concentration) and rate of production by decreasing the requirement for ATP turnover during biosynthesis. 

It is also reasonable to assume that the rate of ATP turnover is similar on different carbon sources. 

Figure 2. Force generation and energy metabolism in human quadriceps femoris muscle stimulated intermittently at 20 Hz, with 1.6 sec tetani with 1.6 sec rest periods between tetani. The upper panel shows force, ATP turnover rate, and pH the middle panel, the concentrations of PCr, P and lactate and the lower panel, ATP, ADP, IMP, H, and calculated H2PO4. From Hultman et al. (1990), with permission from Human Kinetics Publishers.

Figure 2 shows the expected changes during an intense contraction an 80% decrease in force generation and a comparable decrease in ATP turnover rate. The ATP content was decreased by about 40% and PCr by 95%. At the same time large increases were observed in and P,. 

Katz, A., Sahlin, K., Henriksson, J. (1986b). Muscle ATP turnover rate during isometric contraction in humans. J. Appl. Physiol. 60, 1839-1842. 

Although many effector systems utilise ATP or the equivalent, directly or indirectly, the rate at which ATP is used by such processes is trivial in comparison with many other processes. For example, in rat heart, the rate of cyclic AMP formation and degradation represents only 0.05 per cent of the normal rate of ATP turnover. 

E. L. Lim, K. G. Hollingsworth, P. E. Thelwall and R. Taylor, Measuring the acute effect of insulin infusion on ATP turnover rate in human skeletal muscle using phosphorus-31 magnetic resonance saturation transfer spectroscopy. NMR Biomed., 2010, 23,952-957. 

Figure 5. 31P NMR magnetization transfer measurements of ATP turnover in immobilized yeast cells. A control spectrum is shown in (a). Saturation of the y-phosphate resonance of ATP and transfer of this magnetic label through chemical exchange results in a decrease in the intensity of the P, and sugar phosphate resonances (b). This is most clearly seen in the difference spectrum (a-b). The magnitude of the decrease in the P, resonance can be used to calculate the flux between P, and ATP and, hence, the rate of ATP turnover (see Brindle, 1988a,b).

Brindle, K.M., Blackledge, M.J., Challiss, R.AJ., Radda, G.K. (1989). 31P NMR magnetization transfer measurements of ATP turnover during steady state isometric contraction in the rat hindlimb in vivo. Biochemistry 28,4887-4893. 

Figure 4. Half-cycles in dissipative (d) maintenance metabolism with steady-state ATP turnover, decoupled by futile cycling with, in this example, fructose 6-phos-phate/fructose 1,6-bisphosphate. The net enthalpy change is calculated exclusively due to the catabolic half-cycle because both the ATP and the futile cycles contain equal but opposite exothermic and endothermic components (after Gnaiger, 1990).

To figure out the biological meaning of the crossover (Figure 2.9 (C-E)), we need to know why this occurs. In mammals the answer seems to be a simple conseqence of power obtainable from different metabolic pathways maximum ATP turnover rates supported by fat oxidation in mammals are only about two-thirds the maximum ATP turnover rates supportable by glycogen oxidation (figure 2.10). The reasons for... 

ADP monitored simultaneously in human gastrocnemius and soleus during three different exercise intensities, 20%, 30%, and 40% of maximum (bars), with rest periods in between and recovery at the end of the protocol. To standardize the data, PCr and ATP are expressed as the ratios of each to the sum of easily MRS-measurable phosphate metabolites [PCr] + [ATP] + [Pi], while ADP is given in molar units, since it is calculated from the CPK equilibrium. Left panels in A, B, and C indicate representative MRS data. Right panels show plots of work intensity (% maximum ATP turnover rate) as the independent parameter and metabolite concentrations at the end of each work bout are plotted as dependent parameters (on the vertical axes). (Modified from Allen et al., 1997.)... 

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