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

摘要

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 deg C over 10 min, and a Km of 0.26 mM. The partially purified enzyme was activated by 10 mM Mg~(2+) up to 168% of the original activity, while Zn~(2+), Mn~(2+) and Cu~(2+) ions, chelating agent (EDTA) and NaN_3 (1-10 mM), and 5'-ribonucleotides (1-5 mM) were inhibitory. Final enzyme preparation was stable over 8 d at 4 deg C), at 70 deg C for up to 120 min and without loss of activity over 90 d at -18 deg C.