Partial purification and biochemical characterization of alkaline 5'-phosphodiesterase from barley malt sprouts

An alkaline 5-phosphodiesterase (5-PDE) from barley (Hordeum distichum) malt sprouts was partially purified by thermal treatment and acetone precipitation to diminish phosphomonoesterase (PME) activity. 5-PDE was purified 40-fold to a specific activity of 30 U mg^–1 protein with a final yield of about 32%. With synthetic substrate, the enzyme had an optimum pH of 8.9, maximum activity at 70 °C over 10 min, and a Km of 0.26 mM. The partially purified enzyme was activated by 10 mM Mg²⁺ up to 168% of the original activity, while Zn²⁺, Mn²⁺ and Cu²⁺ ions, chelating agent (EDTA) and NaN₃ (1–10 mM), and 5-ribonucleotides (1–5 mM) were inhibitory. Final enzyme preparation was stable over 8 d at 4 °C), at 70 °C for up to 120 min and without loss of activity over 90 d at –18 °C.