Antitumor glycogen from scallops and the interrelationship of structure and antitumor activity

Hot water extract of scallop was treated with actinase E and fractionated by Sephadex G-25 gel-filtration and DEAE Sephadex A-25 ion-exchange chromatography. The antitumor activity of these fractions against Meth-A fibrosarcoma was examined. The nonadsorbed fraction (SCA25A) and weakly adsorbed fraction (SCA25B) obtained on DEAE Sephadex A-25 anion-exchange gel showed strong antitumor activity. Chemical analyses and NMR spectra identified SCA25A and SCA25B as glycogen. However, glycogen extracted from the scallop with trichloroacetic acid and from abalone showed no antitumor activity. This difference was thought to be due to variations in the fine structure of the glycogen molecule. The fine structure of glycogen was investigated by a sequential enzyme digestion method using beta-amylase and pullulanase, while the unit chain was analyzed by high performance anion exchange chromatography. The results showed that the antitumor active glycogen was highly branched with a shorter chain than glycogens without antitumor activity.