High substrate affinity and GTP insensitive AMP deaminase from frog liver

1. Relatively high activity of AMP deaminase (2.5 mumol/min/g wet wt of tissue) estimated at 70 microM AMP concentration was found in frog liver. 2. The enzyme was purified to homogeneity, its subunit and native protein molecular weights were about 70,000 and 330,000 respectively. The specific activity of the purified enzyme was 44 mumol/min/mg of protein at 70 microM AMP and Km for AMP was 0.7 mM. 3. The enzyme was rather specific for AMP, several structural analogues of 5'AMP were deaminated at the rate not exceeding 5% of the rate of AMP deamination. 4. Frog liver AMP deaminase was activated by monovalent cations, highest rate of reaction was observed in the presence of potassium, rhubidium and sodium ions. The enzyme was activated by ADP and ATP and inhibited by inorganic phosphate but was not influenced by GTP.