Characterization of Acid Phosphatase from Welsh Onion

Acid phosphatase (EC 3.1.3.2) from Welsh onion was partially purified by Sephacryl S-200 gel filtration and CM-Sepharose CL-6B ion exchange chromatography. The optimum pH and temperature of acid phosphatase from green onion were pH 5.5 and , respectively. The enzyme was the most stable at pH 6.0 and unstable above pH 9.0. The activation energy of the enzyme was determined to be 4.86kcal/mole. The enzyme utilized p-nitrophenyl phosphate most as a best substrate among tested possible substrates, while 5'-GMP and 5'-IMP were poor substrates for the enzyme. of the enzyme with p-nitrophenyl phosphate as a substrate was identified as 0.87mM. Among metal ions and inhibitors tested, , molybdate and metavanadate ions inhibited the enzyme reaction drastically.