Studies on Violet-colored Acid Phosphatase of Sweet Potato

Abstract

The violet-colored acid phosphatase [EC 3.1.3.2] was purified from sweet potato tubers. The most purified preparation was found to be homogeneous by electro-phoresis and ultracentrifugation. Concentrated solutions of the highly purified enzyme had an intense violet color with a broad absorption between 410 mμ and 700 mμ. The peak was at around 555 mμ. The enzyme activity was lost following a variety of treatments in parallel with the disappearance of the absorbance in the visible region. Manganese, magnesium, boron, and silicon were detected in the purified enzyme preparation by emission spectroscopy. The molecular weight was estimated to be approximately 105,000 and 110,000 by sedimentation equilibrium and gel filtration on Sephadex G-200, respectively. Polyacrylamide gel disc electrophoresis in the presence of sodium dodecyl sulfate suggested that the enzyme dissociated into subunits with a molecular weight of approximately 55,000. An isoelectric point determined from the electrofocusing experiments was near 5.0.