Characteristics of levan fructotransferase from Arthrobacter ureafaciens K2032 and difructose anhydride IV formation from levan.

A microorganism producing levan fructotransferase was isolated from sugar-disclosed soil and it was identified as Arthrobacter ureafaciens. The major product from levan by enzyme reaction was identified as di-D-fructofuranose 2,6':6,2' dianhydride by mass spectrometry, nuclear magnetic resonance, and chemical analyses. Small amounts of several oligosaccharides and free fructose were also formed by enzyme reaction. An extracellular enzyme that produces di-D-fructofuranose 2,6':6,2' dianhydride from levan was purified from the culture broth of A. ureafaciens K2032. The enzyme had optimum activity around pH 5.8 and 45 degrees C and had a dimeric form in solution. The N-terminal amino acid residues of the purified enzyme were SAPGSLRAVYHMTPPSGXLXDPQ. The enzyme has narrow substrate range and converts the levan to di-D-fructofuranose 2,6':6,2' dianhydride with around 62.5% conversion yield.