Abstract
Lactobacillus plantarum KSK-II was the most potent oxalate decomposer among various isolated lactic acid bacteria. There was no detectable extracellular or even intracellular oxalate decarboxylase (OxDcase) productivity in the absence of oxalate. The highest enzyme productivity was obtained at 72 h in a medium containing 0.1 M oxalate, 0.1% (w/v) D-glucose, 0.05% (w/v) soybean flour and 0.1% (w/v) of the prebiotics fructo-oligosaccharides and arabinogalactan. Enzyme purification increased its specific activity to 19.6-fold with 14.8% recovery and molecular weight of 63 kDa. The optimal reaction temperature, pH and pI values for OxDcase were 35 degrees C, 5.0 and 3.5 respectively, and it was stable till 70 degrees C and at pH 4.0-7.0 for 1 h. The apparent Km value of the enzyme was 12.70 mM, the turnover number (K-cat) was 64.10 s(-1) and the catalytic efficiency (K-cat/K-m) was 5.05 mM(-1) s(-1). Treatment of oxaluric rats with L. plantarum KSK-II and a prebiotic mixture significantly decreased oxalate levels inside their bodies suggesting a successful synbiobtic system in the prevention of oxalate stones. KSK-II OxDcase may also be clinically significant from the perspective of its thermo-tolerance and activation by triton X-100 and the reducing agents (sodium-L-ascorbate, potassium ferrocyanide and o-PDA). The non-inhibitory activity of chloride and the oxalate specificity are also significant for clinical applications of the enzyme in measuring of oxalate levels in body fluids.