Hypoxia increases the activity of xanthine oxidase (XO) and its precursor, xanthine dehydrogenase (XDH), but the mechanism of regulation is unclear. In hypoxic Swiss 3T3 cells, an early (0-24 h) cycloheximide-insensitive increase in XO-XDH activity, coupled with a lack of increase in de novo XO-XDH synthesis (immunoprecipitation) or mRNA levels (quantitative RT-PCR), demonstrated a posttranslat...

Xanthine dehydrogenase (XDH) is a ubiquitous enzyme involved in purine metabolism which catalyzes the oxidation of hypoxanthine and xanthine to uric acid. Although the essential role of XDH is well documented in the nitrogen-fixing nodules of leguminous plants, the physiological importance of this enzyme remains uncertain in non-leguminous species such as Arabidopsis. To evaluate the impact of ...

OBJECTIVE We have previously demonstrated that endothelial xanthine oxidase (XO) levels are dependent on the NADPH oxidase. We postulated that H2O2 may modulate the irreversible conversion of xanthine dehydrogenase (XDH) to XO and sought to examine mechanisms involved. METHODS AND RESULTS H2O2 (100 micromol/L) decreased bovine aortic endothelial cell (BAEC) XDH protein expression, and metabol...

Rhodobacter capsulatus xanthine dehydrogenase (XDH) forms an (alphabeta)2 heterotetramer and is highly homologous to homodimeric eukaryotic XDHs. The crystal structures of bovine XDH and R. capsulatus XDH showed that the two proteins have highly similar folds. We have developed an efficient system for the recombinant expression of R. capsulatus XDH in Escherichia coli. The recombinant protein s...

From a collection of electrophoretic variants of XDH obtained from laboratory strains and natural populations, a stock was isolated that was associated with much greater than normal levels of XDH activity. Preliminary recombination experiments demonstrated that this character maps to the rosy locus. While a series of observations failed to relate this phenotype to alteration in the structure of...

These studies examined the kinetic and mechanistic parameters of mitomycin C (MMC) bioreduction by xanthine dehydrogenase (XDH), an enzyme recently shown to be capable of MMC activation. The bioreduction of MMC by XDH leads to the formation of 2,7-diaminomitosene (2,7-DM) under both aerobic and hypoxic conditions, with greater 2,7-DM formation observed under hypoxic conditions. The XDH-induced ...

HE activity of xanthine dehydrogenase (XDH) in Drosophila melanogaster is affected by mutations at three loci: ma4 at locus 64ion the X chromosome, ry at locus 52 ion the third chromosome, and lxd at locus 33 ? on the third chromosome. See GLASSMAN (1965) for a discussion of these loci. The ma4 and the ry mutants are deficient in XDH while lzd flies have 20 to 25% of the XDH activity of wild ty...

Excess protein ingested by blood meals of mosquitoes is catabolized by a uricotelic pathway. We have established enzyme activity profiles for xanthine dehydrogenase (XDH), the enzyme that catalyzes uric acid synthesis, and related it to intestinal proteolytic activities in female Aedes aegypti mosquitoes.During the first day after eclosion the meconium containing urate and urea of larval/pupal ...

These studies examined the kinetic and mechanistic parameters of mi tomycin C (MMC) bioreduction by xanthine dehydrogenase (XDH), an enzyme recently shown to be capable of MMC activation. The bioreduc tion of MMC by XDH leads to the formation of 2,7-diaminomitosene (2,7-DM) under both aerobic and hypoxic conditions, with greater 2,7-DM formation observed under hypoxic conditions. The XDH-induce...

In situ hybridization was used to localize xanthine dehydrogenase (XDH) mRNA in horse skeletal muscle. Capillary endothelial cells were found to express XDH, but muscle cells did not give any signal. The digoxigenin-labelled probe was produced by PCR with primers based on the cDNA sequence of mouse XDH and horse lung cDNAs. A 4.3 kb mRNA was detected in a Northern blot.