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

Abstract

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.