Résumé
A non specific acid phosphatase from Aspergillus oryzae NRRL447 catalyzes the phosphate hydrolysis from nicotinamide adenine dinucleotide forming nicotinamide riboside, adenosine and Pi as the final products of the reaction. The enzyme was purified to homogeneity by a sequential treatment of acetone fractionation, DEAE-cellulose chromatography and gel filtration chromatography. The enzyme was purified 400-fold. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of the purified enzyme showed a single protein band of MW 52 kDa. The enzyme displayed maximum activity at pH 5.0 and 40 °C with NAD as substrate. The enzyme activity appeared to be stable over pH 2.0–5.0 and up to 40 °C. The enzyme activity was enhanced slightly by Mg2+, Ca2+ whereas inhibited strongly by F-, Mo04 -, Cu2+ and Fe2+. The enzyme hydrolyzes several phosphate esters, suggesting a probable non-specific nature. The substrate concentration-activity relationship is the hyperbolic type and the apparent Km for NAD+ was 6.25 x 10-4 M.