Dephosphorylation of phytate by using the Aspergillus niger phytase with a high affinity for phytate.

A phytase (EC 3.1.3.8) with a high affinity for phytic acid was found in Aspergillus niger SK-57 and purified to homogeneity in four steps by using ion-exchange chromatography (two types), gel filtration, and chromatofocusing. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the purified enzyme gave a single stained band at a molecular mass of approximately 60 kDa. The Michaelis constant of the enzyme for phytic acid (18.7 +/- 4.6 microM) was statistically analyzed. In regard to the orthophosphate released from phytic acid, a significant difference between a low K(m) phytase from A. niger SK-57 and a high K(m) phytase from Aspergillus ficuum was recognized.