STRUCTURE AND DISTRIBUTION OF GLUCOMANNAN AND SULFATED GLUCAN IN THE CELL WALLS OF THE RED ALGA <i>KAPPAPHYCUS ALVAREZII</i> (GIGARTINALES, RHODOPHYTA)

Abstract

Two new polysaccharides were isolated from the cell walls of the carrageenan producing red seaweed Kappaphycus alvarezii (Doty) Doty. They were characterized by chemical analyses, enzymatic degradations, and nuclear magnetic resonance spectroscopy. One was a 4.0 M NaOH soluble β‐(1,4)‐ d ‐glucomannan that mostly precipitated upon neutralization and dialysis. It was composed of about 82 residues, and 70% of its glucose and mannose were released by a commercial cellulase enzyme complex. The disaccharide β‐ d ‐Man (1→4) d ‐Glc was recovered from the hydrolysate during the first hours of degradation and confirmed the chemical structure of the polysaccharide. The other polysaccharide was extracted with 1.5 M NaOH and was identified as a sulfated glucan of degree of polymerization of about 180 1,4‐linked β‐glucose containing 10% 1,3‐linkages. The sulfate was located on C‐6 of 64% of the 4‐linked glucose residues. A third alkali‐soluble polysaccharide rich in galactose was also detected. The distribution of the glucomannan and galactose containing polysaccharides was inversely related to the algal cell size. Potential functions of these alkali‐soluble polymers are discussed in the context of cell wall polysaccharide assembly.