Lushchak, V.I. and Storey, K.B. 1994. Effect of exercise on the properties of AMP-deaminase from trout white muscle. Int. J. Biochem. 26, 1305-1312.

EFFECT OF EXERCISE ON THE PROPERTIES OF AMP-DEAMINASE FROM TROUT WHITE MUSCLE


V.I. Lushchak and K.B. Storey


ABSTRACT
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) and 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.