Regulation of AMP-deaminase activity from white muscle of common carp Cyprinus carpio

AMP-deaminase was purified to electrophoretic homogeneity from white skeletal muscle of a teleost fish, the common carp, Cyprinus carpio. The purified enzyme was highly stable and showed non-Michaelis-Menten kinetics with a S-0.5 value for AMP of 2.52 +/- 0.16 mM (SEM) and a Hill coefficient of 1.19 +/- 0.11. Specific activity of the purified enzyme was 1000-1200 U/mg protein. The pH optimum was 6.3 and the enzyme was activated by ADP and ATP, but inhibited by phosphate and fluoride. Low concentrations of NaCl and KCl (100-150 mM) activated, whereas higher concentrations were inhibitory. Free radicals inactivated the enzyme, decreasing V-max by one-half but not affecting S-0.5 or Hill coefficient. Possible regulatory mechanisms of AMP-deaminase activity in fish muscle are discussed. (C) 2007 Elsevier Inc. All rights reserved.