Fine chemical structure analysis of oligosaccharides produced by an ulvan-lyase degradation of the water-soluble cell-wall polysaccharides from Ulva sp. (Ulvales, Chlorophyta)

A marine bacterium degrading the water-soluble cell wall polysaccharides from Ulva sp. (ulvan) has been isolated. The good correlation between ulvan degradation monitored by reducing-power, UV absorbance and viscosimetry, indicated that the crude enzymatic extract contains essentially an endo-ulvan lyase activity. This activity was rapidly inhibited by the reaction products which consisted of a series of ulvanobiouronic acid A 3-sulfate [→ 4)-β-d-GlcpA-(1 → 4)-α-l-Rhap 3-sulfate-(1 → ]n with 4-deoxy-l-threo-hex-4-enopyranosiduronic acid at the non-reducing end. Other deviant repeating structures with β-d-Xylp or α-l-IdopA replacing β-d-GlcpA in the repeating ulvanobiouronic acid disaccharide and the presence of two consecutive (1 → 4) linked β-d-GlcpA demonstrated the great variability and complexity of ulvan chemical structure.