METABOLISM OF NUCLEOSIDES IN BACTERIA .10. PURIFICATION, CRYSTALLIZATION, AND SOME PROPERTIES OF XANTHINE DEHYDROGENASE FROM PSEUDOMONAS, SYNXANTHA A-3

A xanthine-oxidizing enzyme in a strain of Pseudomonas synxantha was purified and isolated as a crystalline preparation. The purification procedure involved ammonium sulfate fractionation, column chromatographies on DEAE-ce1lulose, DEAE-Sephadex A-50 and Sephadex G-200, and crystallization in the presence of ammonium sulfate. The crystalline enzyme was homogeneous by the criteria of ultracentrifugation and polyacrylamide gel electrophoresis. The enzyme was reddish brown and showed a characteristic absorption spectrum: it had absorption maxima at around 270 and 450 nm with shoulders at 385, 425, and 550 nm. The enzyme was determined to have a molecular weight of about 540,000, and to contain nonidentical subunits with molecular weight of 76,000 and 54,000. The enzyme catalyzed the oxidation of hypoxanthine, xanthine, and some purine compounds, and NAD+ acted with it as an effective electron acceptor. The enzyme reaction was inhibited by some metal ions, such as Hg2+, Ag+, and Cu2+, and KCN. © 1979 Taylor & Francis Group, LLC.