Regulation of АМР-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 S0.5 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 Vmax by one-half but not affecting S0.5 or Hill coefficient. Possible regulatory mechanisms of AMP-deaminase activity in fish muscle are discussed.