Effect of Subacute Intoxication with Nitrite on AMP-Deaminase Activity in Skeletal Muscles of Common Carp (Cyprinus carpio)

This study was aimed to evaluate the effects of intoxication of common carp with nitrite on some properties of Adenosine 5'-monophosphate (AMP) deaminase in the skeletal muscle. LC50 value was determined to be 512 mg/L. After estimating the LC50, fish were exposed to 153 mg/L (30% LC50) and sampling was done at 0, 24, 48, 72, and 96 h after exposure. Cytosolic AMP deaminase was purified from the skeletal muscle of the control and experimental groups. AMP-deaminase showed Hill kinetics with an S-0.5 value for AMP of 2.52 +/- 0.031 and 1.45 +/- 0.07 mM, a Hill coefficient (n(H)) of 1.35 +/- 0.051 and 1.79 +/- 0.60, and a maximal velocity (V-max) of 133.39 +/- 28 and 98.9 +/- 38 IU/mg protein for the control and experimental groups, respectively after 96 h. The optimum pH was reduced during nitrite intoxication. The maximal activation of the enzyme was at 45 degrees C. Also, activation energy declined in the experimental groups. Fenton reaction showed that the enzyme was tolerant to free radicals. According to the results, AMP deaminase activity in the common carp's muscles increased following nitrite intoxication. Also, acidic condition increased AMP deaminase activity that could be an adaptive response to hypoxic condition caused by nitrite intoxication.