Oyster Glycogen: Fine Structure and Enzymic Degradation

Abstract

Glycogen was prepared from the fresh oysters (Crassostrea gigas) , collected every month from June 1990 to April 1991, cultured in Hiroshima bay, and the precise α-1, 4-unit-c:hain distributions of different glycogen preparations were analyzed by high performance anion exchange chromatography (HPAEC) after complete debranchi昭 withisoa町 lase.The unit chains of the glycogen, in average chain length (CL) , 10~11 was found to distribute in a range of G2-G35 (G7-G12, predominant) . However, there was a distinct difference in the pattern of unit-chain distributions between summer (spawning season) and autumn to winter (edible season). The fine structure of oyster glycogen (A : B-chains, 0.7 : 1) was elucidated mainly by repeating of the enzymic trimming, which involved in stepwise degradation by β-amylase and pullulanase, and quantitative analysis by HPAEC. The result showed that the multi-branched spherical molecule might be formed by 5 or 6 times inter-linking of the unit-chains (B-chains).

In the nutritional view point, the oyster glycogen was hydrolyzed by salivaly (human) and/ or pancreatic (hog) α-amylase, and the enzymic digest (amylolysis limit, 48 % ) was analyzed by HPAEC. There were produced a variety of maltosaccharides including double branched oligosaccharides. They were gradually hydrolyzed by the intestinal glucosidase (rat) to glucose, though small amounts of branched oligosaccharides appear to remain as non-digestible saccharides.