Heterogeneity of Alginate in Special Reference to the Enzymatic Degradation

Abstract

Alginate preparation from Ishige okamurai YENDO was fractionated with magnesium chloride and ethanol into three fractions; guluronic acid rich (G-), mannuronic acid rich (M-) and intermediate (MG-) fractions, although they did not seem homogeneous upon gel-filtration. Digestion of these alginates with either polymannuronide or poly-guluronide lyase left alginate-like polyuronides (residual alginates) which were richer in guluronic or mannuronic acid residue, and were not only heterogeneous on gel-filtration but also very different in their average chain length. The guluronic acid rich residual alginates from the polymannuronide lyase digest of MG-fraction was degraded by polyguluronide lyase extensively to di- and triuronides, while higher oligouronides were produced beside them from M- and G-fractions. Thus, it was shown that the alginic acid molecules of this alga were heterogeneous in the localization of each kind of uronic acid residue as well as in its proportion.