Ontogenetic profile of ecto-5′-nucleotidase in rat brain synaptic plasma membranes

► AMP hydrolyzing activity in synaptic plasma membranes (SPM) increases with ontogeny stage. ► In contrary, ecto-5′-nucleotidase protein in the SPM displayed the reverse pattern of expression. ► The increase in enzyme activity with maturation was completely due to the increase in the enzyme catalytic efficiency. ► Direct immunocytochemical evidence of colocalization between presynaptic marker syntaxin and ecto-5′-nucleotidase.