| Abstract: | Basic ascorbate oxidase of the multiple enzyme forms existing in young fruit of satsuma mandarin (Citrus unshiu Marc) has been separated and subsequently purified to electrophoretic homogeneity through (NH4)2SO4 fractionation and chromatographies on DEAE-Toyopearl 650M, CM-Sephadex C-50 and Sephadex G-100. The native molecular weight was estimated to be 141 kDa by gel filtration and composed of two non-identical subunits with an apparent mass of 74 kDa and 62 kDa. The optimum pH was found to be 5.5 with reasonable stability between pH 5 and 8. The enzyme had an optimum temperature at 45°C and was stable up to 50°C upon heat treatment for 5 min. The presence of sodium diethyldithiocarbamate, metabisulphite and potassium cyanide completely inhibited the enzyme activity. Fluoride also inhibited the activity substantially at higher concentrations. Other tnonovalent and divalent metal ions did not have inhibitory effects. |
