RESUMO
An oxalate oxidase was purified to apparent homogeneity from the leaves of 10-days old seedlings of forage Sorghum (Sorghum vulgare var. KH-105). The enzyme had a Mr of 124 kDa with two identical subunits, an optimum pH of 4.5, optimum temperature of 37 degrees C and activation energy (Ea) of 2.0338 Kcal/mol. The rate of reaction was linear up to 7 min. K(m) value for oxalate was 0.22 mM. The enzyme was stimulated by Cu2+ and inhibited by EDTA, NaCN, diethyldithiocarbamate, Na2SO4, but unaffected by NaCl at 0.1 mM concentration. Although the enzyme was stimulated by flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD), UV and visible spectra of the enzyme did not match with that of a flavoprotein. The positive reaction of the enzyme with orcinol-H2SO4 reagent indicated its glycoprotein nature. The superiority of the purified enzyme over earlier reported oxalate oxidases for determination of urinary oxalate has been demonstrated.
