Effect of exercise on the properties of AMP-deaminase from trout white muscle
AMP-deaminase was purified to homogeneity from white skeletal muscle of control (resting) and exercised (1 min burst swimming) rainbow trout, Oncorhynchus mykiss. The enzyme showed a subunit molecular weight of 71,600 ± 550 kD, a Km AMP of 1.6-1.8 mM at pH 7, and was affected by allosteric inhibitors (GTP, IMP) amd activators (ADP, ATP). AMP-deaminase was inhibited by MgSO4 but activated by low concentrations of NaCl and KCl (100-150 mM); higher KCl was inhibitory. Exercise resulted in a stable modification of some properties (possibly via reversible phosphorylation); I50 values for IMP decreased by 65% and activation energies (from Arrhenius plots) changed significantly. Other properties were affected by assay pH: Km AMP decreased by 50% and Ka, ADP decreased by 70% when pH was lowered from pH 7.3 (typical of resting muscle) to pH 6.6 (muscle pH after exhaustive exercise). The data suggest that a stable modification of AMP-deaminase during exercise, coupled with effects of reduced cytosolic pH, could enhance enzyme function in the rapid conversion of AMP to IMP in working fish muscle.
|Journal||International Journal of Biochemistry|
Lushchak, V.I., & Storey, K. (1994). Effect of exercise on the properties of AMP-deaminase from trout white muscle. International Journal of Biochemistry, 26(10-11), 1305–1312. doi:10.1016/0020-711X(94)90100-7