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 polysaccharid es from Ulva sp. (ulvan) has been isolated. The good correlation betwe en ulvan degradation monitored by reducing-power, UV absorbance and vi scosimetry, indicated that the crude enzymatic extract contains essent ially an endo-ulvan lyase activity. This activity was rapidly inhibite d by the reaction products which consisted of a series of ulvanobiouro nic acid A 3-sulfate [--> 4)-beta-D-GlcpA-(1 --> 4)-alpha-L-Rhap 3-sul fate-(1 -->]n with 4-deoxy-L-threo-hex-4-enopyranosiduronic acid at th e non-reducing end. Other deviant repeating structures with beta-D-Xyl p or alpha-L-IdopA replacing beta-D-GlcpA in the repeating ulvanobiour onic acid disaccharide and the presence of two consecutive (I --> 4) l inked beta-D-GlcpA demonstrated the great variability and complexity o f ulvan chemical structure. (C) 1997 Elsevier Science Ltd. All rights reserved.