Truncational analysis of rat urate oxidase in insect cells

Molecular cloning and expression of uricase gene from Arthrobacter globiformis in Escherichia coli and characterization of the gene product

Arthrobacter globiformis FERM BP-360 produces uricase (urate oxidase; EC 1.7.3.3) intracellularly. A genomic library of the bacterium, prepared in the plasmid vector pUC118, was screened with probes based on the amino acid sequence of the purified uricase. We found that a chimeric plasmid in the library, designated pUOD1, carries a 2.0-kb DNA insert from the Arthrobacter DNA that hybridizes with the probe. The DNA insert contains an ORF consisting of 302 amino acids with a calculated molecular mass of 33,858. The protein translated from the ORF displays the highest identity (67%) to uricase from a bacterium, Cellulomonas flavigena. X-ray fluorescence analysis showed that the Arthrobacter uricase contains copper ion. However, we found that the catalytic activity of uricase is inhibited by the excessive addition of copper ion. Although the production of A. globiformis uricase is induced by the addition of uric acid to the culture medium, Escherichia coli harboring pUOD1 produced 20-fold higher uricase than the original Arthrobacter strain, even without an inducer.

Cloning, sequence analysis and expression in Escherichia coli of the gene encoding a uricase from the yeast-like symbiont of the brown planthopper, Nilaparvata lugens

A urate oxidase (uricase; EC 1.7.3.3) gene of the yeast-like fungal endosymbiont of the brown planthopper, Nilaparvata lugens, was cloned, and sequenced together with its flanking regions. The gene comprised a open reading frame of 987 bp, that was split into two parts by a single 96 bp intron. The encoded uricase was 296 amino acids with 62% sequence identity with that of Aspergillus flavus. The molecular weight deduced was 32,882, and the predicted isoelectric point was 6.06. The symbiont's uricase conserved all the known consensus motifs, except the C-terminal PTS-1, Ser-basic-Leu. The leucine at the third position of PTS-1 was replaced by serine in the C-terminus of the symbiont's uricase. The symbiont's uricase gene was successfully expressed in Escherichia coli, and the product, tagged with histidine residues, was purified. The symbiont's uricase, thus produced, was as active as those from plants and animals, but less active than those from other fungi.