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.
International Journal of Biochemistry
Department of Biology

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