Adenosine monophosphate (AMP) deaminase was purified from jumbo squid mantle muscle by chromatography in cellulose phosphate, Q-Fast and 5′-AMP sepharose. Specific activity of 2.5U/mg protein, 4.5% recovery and 133.68 purification fold were obtained at the end of the experiment. SDS–PAGE showed a single band with 87kDa molecular mass, native PAGE proved a band of 178kDa, whereas gel filtration detected a 180kDa protein, suggesting the homodimeric nature of this enzyme, in which subunits are not linked by covalent forces. Isoelectric focusing of this enzyme showed a pI of 5.76, which agrees with pI values of AMP deaminase from other invertebrate organisms. AMP deaminase presented a kinetic sigmoidal plot with V max of 1.16μM/min/mg, K m of 13mM, K cat of 3.48μM.s −1 and a K cat /K m of 267 (mol/L) −1 .s −1 . The apparent relative low catalytic activity of jumbo squid muscle AMP deaminase in the absence of positive effectors is similar to that reported for homologous enzymes in other invertebrate organisms.