title: The enzymes involved in the synthesis of phytic acid in Lemna gibba (studies on the biosynthesis of cyclitols, XL.(1)).
abstract: The biosynthesis of phytic acid is known to be catalyzed by enzymes causing a stepwise phosphorylation of myo-inositol or 1L-myo-inositol 1-phosphate with adenosine triphosphate as phosphate donor. The kinase responsible for these phosphorylations in Lemna gibba were purified by affinity chromatography on a Sepharose gel carrying myo-inositol 2-phosphate at the binding site. Three fractions with enzymatic activity could be identified; in the first one, we find myo-inositol kinase (EC 2.7.1.64) phosphorylating myo-inositol to 1L-myo-inositol 1-phosphate; the second one brings about the phosphorylation of myo-inositol trisphosphate to phytic acid; the third one phosphorylates myo-inositol 1-phosphate to a myo-inositol trisphosphate. An enzyme oxidizing 1L-myo-inositol 1-phosphate to an uronic acid derivative is found in the first two fractions. In the presence of ATP, Mg2+, Mn2+, and the second and the third enzyme fractions in an appropraite mixture, 1L-myo-inositol 1-phosphate can be phosphorylated to phytic acid. The structure of the trisphosphate acting as an intermediate is not yet known.
mesh_terms: D002999:Clone Cells / Q000378:metabolism; D004590:Electrophoresis, Paper; D004591:Electrophoresis, Polyacrylamide Gel; D007295:Inositol Phosphates / Q000378:metabolism; D010770:Phosphotransferases / Q000302:isolation & purification* / Q000378:metabolism; D010833:Phytic Acid / Q000096:biosynthesis*; D010944:Plants / Q000378:metabolism*
chemical_list: D007295:Inositol Phosphates; D010833:Phytic Acid; D010770:Phosphotransferases