2.3.1.12 -18°C, 0.05 mM potassium phosphate buffer, pH 7.0, 0.5 mM EDTA, more than 6 months 2.3.1.12 liquid nitrogen, 50 mM potassium phosphate buffer pH 7.0, 0.5 mM EDTA, 0.05 mM phenylmethylsulfonylfluoride