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 V_max of 1.16 μM/min/mg of protein, K_m of 1.49 mM, K_cat of 3.48 μM of P_ι s^-1 and K_cat/K_m relation of 356.52 ((mol/L)^-1 s^-1). Purified enzyme preferred AMP as substrate (by 6.7-folds) than IMP, showing a K_m of 6.34 mM, V_max of 0.19 μM/min/mg of protein a K_cat of 0.3388 mol of P_ι s^-1 and K_cat/K_m relation of 53.44 ((mol/L)^-1 s^-1). The low K_m in relation to purified AMP deaminase of the same organism suggested a high contribution of 5′-nucleotidase in AMP degradation in jumbo squid mantle.