Fructose polysaccharides and oligosaccharides are gaining strong importance due to their beneficial effects on human health and their applications in the food, feed and pharmaceutical industries. Fructan synthesis has been characterised in a wide variety of bacteria and plants. Metagenomic DNA sequence data suggests that several archaeal strains also contain fructosyltransferase (ftf) genes in their genome sequences (www.cazy.org), and thus may be able to synthesise fructans. The archaeal ftf genes are predicted to encode glycoside hydrolase family 68 enzymes. These genes are of strong interest in view of their potential role in the synthesis of novel prebiotic compounds. In the present studies, we have expressed putative ftf gene of an archaeon Halalkalicoccus jeotgali B3T in E. coli. The recombinant enzyme produced water-insoluble polysaccharide using sucrose as a substrate. Analysis by 13C and 1H NMR spectroscopy revealed the polysaccharide to be an inulin-type fructan polymer, depicting that the GH68 gene of H. jeotgali B3T codes for an inulosucrase enzyme. This is the first report on heterologous expression of an archaeal inulosucrase gene, which also provides conclusive evidence of the functional identity of this gene.
- glycoside hydrolase
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