Expression of the gene encoding oxalate decarboxylase from Bacillus subtilis and characterization of the recombinant enzyme

Background: The concentration of urinary oxalate is more influential to the formation of calcium oxalate urolithiasis than is urinary calcium concentration. YvrK gene encodes a 43 KD-sized oxalate decarboxylase. We previously developed the recombinant Escherichia coli (E. coli) expressing Yvrk gene from Bacillus subtilis and named it as pBy. The aim of this study was to purify the recombinant oxalate decarboxylase overexpressed in E.

Results: The oxalate-degrading activity of pBy was highest when cultured at pH 5. The activity of purified oxalate decarboxylase was determined after incubation with sodium oxalate and the optimal pH and temperature of oxalate decarboxylase were determined. Purified oxalate decarboxylase degraded more than 50% of oxalate when incubated with MnCl₂ and sodium oxalate in atmospheric O₂. The optimal pH of recombinant oxalate decarboxylase was 5 and the optimal temperature was 28°C. Eight-week-old Sprague-Dawley male rats were used as a transient hyperoxaluric rat model. Suprapubic catheter was inserted into the bladder of each rat and urine was collected hourly before and 3 hours after oral oxalate intake in the absence and presence of homogenates of pBy and non-recombinant E. coli as the control. After the oral intake of sodium oxalate, the concentration of oxalate in urine increased exponentially for 3 hours. The oxalate concentration in urine was decreased significantly by pBy homogenates compared to control.

Conclusions: We constructed the recombinant E. coli expressing YvrK gene and purified the recombinant oxalate decarboxylase successfully. Purified recombinant oxalate decarboxylase, as well as recombinant E. coli named pBy, showed the oxalate-degrading activity in in vitro and in vivo model.