title: Characterization of phytase produced by Aspergillus niger.
abstract: The extracellular activity of Aspergillus niger phytase at the end of the growth phase was 132 nkat/mL in a laboratory bioreactor. The purified enzyme has molar mass approximately 100 kDa, pH optimum at 5.0, temperature optimum at 55 degrees C and high pH and temperature stability. The Km for dodecasodium phytate, calcium phytate and 4-nitrophenyl phosphate are 0.44, 0.45 and 1.38 mmol/L, respectively. The enzyme is noncompetively inhibited by inorganic monophosphate (Ki = 2.85 mmol/L) and by Cu2+, Zn2+, Hg2+, Sn2+, Cd2+ ions and strongly by F- ones; it is activated by Ca2+, Mg2+ and Mn2+ ions. The substrate specificity of phytase is broad with the highest affinity to calcium phytate.
authors.affiliation: Institute of Microbiology, Academy of Sciences of the Czech Republic, Prague, Czech Republic.
authors.forename: J
authors.initials: J
authors.lastname: Dvoráková
authors.forename: O
authors.initials: O
authors.lastname: Volfová
authors.forename: J
authors.initials: J
authors.lastname: Kopecký
mesh_terms: D010832:6-Phytase / Q000037:antagonists & inhibitors / Q000302:isolation & purification* / Q000378:metabolism; D001234:Aspergillus niger / Q000201:enzymology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005656:Fungal Proteins / Q000037:antagonists & inhibitors / Q000302:isolation & purification* / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008970:Molecular Weight; D010833:Phytic Acid / Q000378:metabolism; D013379:Substrate Specificity; D013696:Temperature
chemical_list: D004791:Enzyme Inhibitors; D005656:Fungal Proteins; D010833:Phytic Acid; D010832:6-Phytase