AMP-deaminase from sea scorpion white muscle: properties and redistribution under hypoxia

AMP-deaminase was purified from the white muscle of the teleost sea scorpion, Scorpaena porcus but due to high instability of the pure enzyme, routine analysis of enzyme properties were conducted: with partially purified preparations. The enzyme showed non-Michaelis-Menten kinetics 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 velocity (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 mu M for GTP end 45 mu M for IMP. Phosphate and fluoride, at low concentrations (up to 2 mM) slightly activated AMP-deaminase, but at higher concentrations became inhibitory. Partial characterization of AMP-deaminase from white muscle of another teleost fish, the corb (Sciena umbra), showed that this enzyme had characteristics very similar to those of the sea scorpion enzyme. In vivo exposure of sea scorpions to hypoxia increased the proportion of AMP-deaminase bound to particular matter 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 effects of allosteric modifiers and enzyme interactions with cellular structural elements. (C) 1998 Published by Elsevier Science Inc. All rights reserved.