The most important cephalopod resource in the northwestern area of Mexico is the jumbo squid whose postmortem biochemical behavior has been studied in detail. Adenosine triphosphate (ATP) degradation in this organism is different than the other species because of the fast degradation of adenosine monophosphate (AMP) metabolite in mantle. In this research, AMP deaminase from jumbo squid mantle was partially characterized. The enzyme showed an optimum behavior at 50 °C, the enzyme lost more than 90% of its activity within 15 min from 55 to 60 °C, and the enzyme remained stable for 30 min from 10 to 50 °C. It was also stable within the pH range of 3.0–5.0 and exhibited an optimum activity at pH 4.5. Enzyme was strongly activated by Mg+2and weakly activated by Ca+2. ATP was an excellent activator even in a low concentration, while adenosine diphosphate (ADP) did it at higher concentrations. These results suggest that enzyme might be regulated by the adenylate energy charge. © 2010 Taylor & Francis Group, LLC.