Isolation and properties of AMP deaminase from jumbo squid (Dosidicus gigas) mantle muscle from the Gulf of California,Mexico

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 2.5 U/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 87 kDa molecular mass, native PAGE proved a band of 178 kDa, whereas gel filtration detected a 180 kDa 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 1.16 μM/min/mg, K_m of 13 mM, K_cat of 3.48 μM.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.