title: Performance of microbial phytases for gastric inositol phosphate degradation.
abstract: Microbial phytases catalyze dephosphorylation of phytic acid, thereby potentially releasing chelated iron and improving human iron absorption from cereal-based diets. For this catalysis to take place in vivo, the phytase must be robust to low pH and proteolysis in the gastric ventricle. This study compares the robustness of five different microbial phytases, evaluating thermal stability, activity retention, and extent of dephosphorylation of phytic acid in a simulated low-pH/pepsin gastric environment and examines secondary protein structural changes at low pH via circular dichroism. The Peniophora lycii phytase was found to be the most thermostable, but the least robust enzyme in gastric conditions, whereas the Aspergillus niger and Escherichia coli phytases proved to be most resistant to gastric conditions. The phytase from Citrobacter braakii showed intermediate robustness. The extent of loss of secondary structure at low pH correlated positively with the extent of activity loss at low pH.
authors.affiliation: Center for BioProcess Engineering, Department of Chemical and Biochemical Engineering, Building 229, Technical University of Denmark , DK-2800 Kgs. Lyngby, Denmark.
authors.forename: Anne Veller Friis
authors.initials: AV
authors.lastname: Nielsen
authors.forename: Christian
authors.initials: C
authors.lastname: Nyffenegger
authors.forename: Anne S
authors.initials: AS
authors.lastname: Meyer
mesh_terms: D010832:6-Phytase / Q000737:chemistry / Q000378:metabolism*; D000595:Amino Acid Sequence; D001234:Aspergillus niger / Q000201:enzymology; D001419:Bacteria / Q000201:enzymology*; D001487:Basidiomycota / Q000201:enzymology; D002942:Circular Dichroism; D004795:Enzyme Stability; D004926:Escherichia coli / Q000201:enzymology; D005753:Gastric Mucosa / Q000378:metabolism; D006358:Hot Temperature; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007295:Inositol Phosphates / Q000378:metabolism*; D010434:Pepsin A / Q000378:metabolism; D017433:Protein Structure, Secondary; D016415:Sequence Alignment; D013270:Stomach / Q000737:chemistry*
chemical_list: D007295:Inositol Phosphates; D010832:6-Phytase; D010434:Pepsin A
keywords: circular dichroism; digestion; enzyme; food; gastrointestinal tract; in vitro; iron; pH stability; pepsin; phytate; phytic acid; proteolysis; secondary structure; thermostability