AMP-DEAMINASE FROM SEA SCORPION WHITE MUSCLE - PROPERTIES AND REDISTRIBUTION UNDER HYPOXIA

AMP-deaminase was purified from the white muscle of the teleost sea sc orpion, Scorpaena porcus but due to high instability of the pure enzym e, routine analysis of enzyme properties were conducted: with partiall y purified preparations. The enzyme showed non-Michaelis-Menten kineti cs with respect to the substrate AMP with a S-0.5 value of 571 +/- 32 mu M, a Hill coefficient (n(H)) of 2.21 +/- 0.24 and a maximal velocit y (V-max) of 176 +/- 22 mu mol/min per mg protein. It was affected by ATP, ADP, GTP and IMP. Half-maximal inhibition was found at about 35 m u M for GTP end 45 mu M for IMP. Phosphate and fluoride, at low concen trations (up to 2 mM) slightly activated AMP-deaminase, but at higher concentrations became inhibitory. Partial characterization of AMP-deam inase from white muscle of another teleost fish, the corb (Sciena umbr a), showed that this enzyme had characteristics very similar to those of the sea scorpion enzyme. In vivo exposure of sea scorpions to hypox ia increased the proportion of AMP-deaminase bound to particular matte r which is :he first such demonstration of an effect of hypoxia on the distribution of this enzyme in animal tissues. The data suggest that AMP-deaminase in sea scorpion muscle is controlled by the combined eff ects of allosteric modifiers and enzyme interactions with cellular str uctural elements. (C) 1998 Published by Elsevier Science Inc. All righ ts reserved.