Isolation and properties of 5′-nucleotidase isolated from jumbo squid (Dosidicus gigas) mantle muscle from the Gulf of California, Mexico

The enzyme 5′-nucleotidase of jumbo squid (Dosidicus gigas) mantle was purified and its SDS–PAGE showed a single band of 33 kDa, whereas a protein with a molecular mass of 107 kDa was detected by gel filtration suggesting a homotrimeric nature of this enzyme. Subunits of the named enzyme were not linked by covalent bonds. Isoelectric focusing of this enzyme showed a pI of 3.6–3.8 and presented a hyperbolic kinetics with Vmax of 1.16 μM/min/mg of protein, Km of 1.49 mM, Kcat of 3.48 μM of Pι s−1 and Kcat/Km relation of 356.52 ((mol/L)−1 s−1). Purified enzyme preferred AMP as substrate (by 6.7-folds) than IMP, showing a Km of 6.34 mM, Vmax of 0.19 μM/min/mg of protein a Kcat of 0.3388 mol of Pι s−1 and Kcat/Km relation of 53.44 ((mol/L)−1 s−1). The low Km in relation to purified AMP deaminase of the same organism suggested a high contribution of 5′-nucleotidase in AMP degradation in jumbo squid mantle.