Isolation and some properties of sorbitol oxidase from Streptomyces sp. H-7775

A sorbitol oxidase (SOX) was found in the cell-free extract of a strain isolated from soil. The strain was classified and designated as Streptomyces sp. H-7775. SOX is constitutively expressed in the cell. The molecular weight of SOX that purified from the cell-free extract was 45,000. The optimum pH and the K(m) for sorbitol were 6.5-7.5 and 0.26 mM, respectively. The prosthetic group was a covalently bound FAD. SOX catalyzed oxidation of D-sorbitol to glucose and hydrogen peroxide without any requirements of exogenous cofactors. SOX did not react with glucose, a reaction product of D-sorbitol. This feature is useful in its application for diagnosis.