MICROBIAL-METABOLISM OF QUINOLINE AND RELATED-COMPOUNDS .8. XANTHINE DEHYDROGENASE FROM A QUINOLINE UTILIZING PSEUDOMONAS-PUTIDA STRAIN

The xanthine dehydrogenase from Pseudomonas putida 86 was purified 68-fold to homogeneity with 47% recovery. SDS-polyacrylamide gel electrophoresis of the enzyme revealed two protein bands corresponding to an M(r) of 87 000 and 52 000. The M(r) of the native enzyme was calculated to 550 000 by gel chromatography. The enzyme contained 4 atoms of molybdenum, 16 atoms of iron, 16 atoms of acid-labile sulphur and 4 molecules of FAD. Due to the composition of the cofactors the xanthine dehydrogenase belongs to the class of molybdo-iron/sulphur-flavoproteins. Form A, an oxidation product of the molybdenum cofactor, was identified. Methanol and cyanide were effective inhibitors.