title: Brain pyridoxine-5-phosphate oxidase. A dimeric enzyme containing one FMN site.
abstract: Pyridoxine-5-phosphate oxidase has been purified 2250-fold from pig brain by affinity chromatography. The enzyme of 60000 molecular weight is made up of two identical size subunits and binds 1 mol of FMN/mol dimer. 1 mol of the fluorescent inhibitor phospho-pyridoxal oxime interacts with 1 mol of the dimeric protein to yield a dissociation constant KD = 0.2 microM. Resolution of the holoenzyme into apoprotein and free FMN does not induce dissociation of the dimeric structure. The oxidase catalyzes the oxidation of the natural substrates pyridoxine 5-phosphate and pyridoxamine 5-phosphate, but phospho-pyridoxyl derivatives of the aromatic carboxylic acids, p-aminobenzoate and m-aminobenzoate, are also excellent substrates of the enzyme. Introduction of electron-withdrawing substituents into the structure of benzene increases the kcat values. A comparison of the kcat values obtained with several synthetic substrates suggests that electron-withdrawing substituents tend to stabilize carbanionic intermediates formed in the earlier stages of catalysis.
mesh_terms: D000818:Animals; D001665:Binding Sites; D001921:Brain / Q000201:enzymology*; D002846:Chromatography, Affinity; D004591:Electrophoresis, Polyacrylamide Gel; D005486:Flavin Mononucleotide / Q000378:metabolism*; D007700:Kinetics; D008970:Molecular Weight; D000587:Oxidoreductases Acting on CH-NH Group Donors / Q000302:isolation & purification*; D011734:Pyridoxaminephosphate Oxidase / Q000302:isolation & purification*; D013050:Spectrometry, Fluorescence; D013552:Swine
chemical_list: D005486:Flavin Mononucleotide; D011734:Pyridoxaminephosphate Oxidase; D000587:Oxidoreductases Acting on CH-NH Group Donors