Acceptor specificity of 4-alpha-glucanotransferases of mammalian glycogen debranching enzymes.
Glycogen debranching enzyme (GDE) has two distinct active sites for its 4-alpha-glucanotransferase and amylo-alpha-1,6-glucosidase activities. The GDE 4-alpha-glucanotransferases of mammals show stringent donor specificity; only alpha-glucans with an alpha-1,6-linked maltotetraosyl or maltotriosyl branch function as donors of a maltotriosyl or maltosyl residue. In this study, we investigated the acceptor specificity of the 4-alpha-glucanotransferases using methyl alpha-maltooligosides, p-nitrophenyl alpha-maltooligosides, and pyridylaminated maltooligosaccharides of various sizes as the acceptor substrates, and phosphorylase limit dextrin as the donor substrate. High-performance liquid chromatography analysis of the transfer products indicated that maltotriosyl and maltosyl residues were specifically transferred from phosphorylase limit dextrin to acceptors with a maltopentaosyl residue comprising a nonreducing-end. These results suggest that the acceptor binding sites in the active sites of mammalian GDE 4-alpha-glucanotransferases are composed of tandem subsites that are geometrically complementary to five glucose residues.
Department of Chemistry, Graduate School of Science, Osaka Prefecture University, Sakai, Osaka 590-0035.
Yasushi
Y
Makino
Kaoru
K
Omichi
D000818:Animals; D001665:Binding Sites; D002417:Cattle; D006004:Glycogen Debranching Enzyme System / Q000737:chemistry* / Q000378:metabolism*; D008099:Liver / Q000201:enzymology; D009844:Oligosaccharides / Q000378:metabolism*; D011817:Rabbits; D013379:Substrate Specificity; D013552:Swine
D006004:Glycogen Debranching Enzyme System; D009844:Oligosaccharides; C021705:maltooligosaccharides; C020569:4 alpha-glucanotransferase