Molecular cloning and expression of a gene encoding a novel sorbitol oxidase from Streptomyces sp. H-7775

A gene encoding a novel intracellular sorbitol oxidase of a soil bacterium, Streptomyces sp. H-7775, was cloned and sequenced. The gene consists of an open reading frame of 1,260-bp encoding a protein of 420 amino acids with a molecular weight of 45,148. Deduced amino acid sequence of the gene has 25.3% identity and 68.1% similarity to that of rat L-gulonolactone oxidase at the overall amino acids. Nucleotide-binding motifs were not found in the deduced amino acid sequence of SOX protein. We succeeded in expressing recombinant sorbitol oxidase with covalently bound FAD in E. coli at about a 4,000-fold higher total enzyme activity than that of the Streptomyces sp. H-7775. The enzymatic properties of the recombinant SOX were similar to those of the enzyme from Streptomyces sp. H-7775. This is the first report of the cloning and expression of a newly categorized enzyme, sorbitol oxidase, from Streptomyces sp.