Preparation and characterization of 5'-phosphodiesterase from barley malt rootlets

Two 5'- phosphodiesterases (5'-PDE-a and 5'-PDE-b) were isolated from barley malt rootlets, and further purified by gel filtration on Sephadex G-25 and Sephadex G-75. 5'-PDE-a had a pH optimum of 5.0, temperature optimum of 70 degrees C, and specific activity of 0.0143 mM x mg(-1) x min(-1). 5'-PDE -b had a pH optimum of 6.0, temperature optimum of 65 degrees C and specific activity of 0.0125 mM x mg(-1) x min(-1). Both enzymes can be used to hydrolyze RNA to form 5'-nucleotides. The enzymes were quite stable at 70 degrees C for 420 minutes. The K(m) was 0.24 mM for 5'-PDE-a and 0.16 mM for 5'-PDE-b with t-RNA (yeast) as substrate.