Abstract
Pyridoxamine (pyridoxine) 5'-phosphate oxidase purified from baker's yeast was found to have a molecular weight of ca. 55, 000 daltons based on polyacrylamide gel electrophoresis. The size of the enzyme subunit was analyzed by gel electrophoresis in the presence of sodium dodecylsulfate. This showed that the enzyme was composed of two nonidentical subunits with a molecular weight of 27, 000 and 25, 000 daltons. Fluorescence titration of the apoenzyme with FMN suggested that the holoenzyme contained one mol of FMN per mot of the enzyme. The Km value of FMN for apoenzyme was calculated to be ca. 16nM on both activities of pyridoxamine 5'-phosphate oxidase and pyridoxine 5'-phosphate oxidase.
