Microbial production of oligosialic acid

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Analyzes and application of sugar in biological process have not been studied extensively. In this regard, we studied microbial production of functional sugar such as oligosialic acids and sialyl lactose, an analog of sialyl Lewis sugar.Seven different bacteriophages were isolated from sewage with Escherichia coli K1 strains as host bacteria. These phages showed specific degrading activity for the host capsular polysaccharide, alpha-2,8-linked polysialic acid. With respect to the minimum substrate size, each enzyme had its own specificity. Of the seven isolated phages, four enzyme showed novel endo-N-acetylneuraminidase activities. We purified one of the enzyme from both phage particle and soluble fraction of infected microbial culture. We also develop an antibody against soluble neuraminidase. In addition to this, the neuraminidase gene was cloned in E.coli and the recombinant protein was purified. By immunoblotting, these 3 neuraminidase species were immunologically identical and their molecular weigh was 90kD.By using normal endothelial cells, we were able to detect inhibitory effects of type specific polysaccharides from Streptococcus agalactiae on adhesion of cancer cells to endothelial cells, which is an essential step of cancer metastasis. The inhibition was probably due to specific structures of the bacterial polysaccharides, since the structures of the saccharides are very similar to those of cancer specific sialyl Lewis carbohydrates (sialyl Le^a and Le^x) which bind to ELAM-1 of endothelial cells.In S.agalactiae strain specific capsular sugar, a ligand (sialyl lactose) was blanched from main chain (repeating units of Gal-GluNAc). The branchings are observed every repeating unit of main chain. We tried to digest the bacterial sugar with a beta-galactosidase and produced sialyl lactose oligomer.