Donor Substrate Specificity of 4- -Glucanotransferase of Porcine Liver Glycogen Debranching Enzyme and Complementary Action to Glycogen Phosphorylase on Debranching
| Autor: | Yumiko Watanabe, Yasushi Makino, Kaoru Omichi |
|---|---|
| Rok vydání: | 2007 |
| Předmět: |
Glycoside Hydrolases
Swine Oligosaccharides Biochemistry Substrate Specificity Glycogen debranching enzyme Glycogen phosphorylase chemistry.chemical_compound Dextrins Glycogen branching enzyme Animals Phosphorylase kinase Glycogen synthase Molecular Biology Chromatography High Pressure Liquid Phosphorolysis chemistry.chemical_classification Binding Sites biology Glycogen Chemistry Glycogen Phosphorylase Glycogen Debranching Enzyme System General Medicine Molecular biology Kinetics Enzyme Liver biology.protein |
| Zdroj: | Journal of Biochemistry. 143:435-440 |
| ISSN: | 0021-924X |
| DOI: | 10.1093/jb/mvm240 |
| Popis: | Glycogen debranching enzyme (GDE) has both 4-alpha-glucanotransferase and amylo-alpha-1,6-glucosidase activities. Here, we examined 4-alpha-glucanotransferase action of porcine liver GDE on four 6(4)-O-alpha-maltooligosyl-pyridylamino(PA)-maltooctaoses, in the presence or absence of an acceptor, maltohexaose. HPLC analysis of digested fluorogenic branched dextrins revealed that in the presence or absence of acceptor, 6(4)-O-alpha-glucosyl-PA-maltooctaose (B4/81) was liberated from 6(4)-O-alpha-maltopentaosyl-PA-maltooctaose (B4/85), 6(4)-O-alpha-maltotetraosyl-PA-maltooctaose (B4/84) and 6(4)-O-alpha-maltotriosyl-PA-maltooctaose (B4/83), whereas 6(4)-O-alpha-maltosyl-PA-maltooctaose (B4/82) was resistant to the enzyme. The fluorogenic product was further hydrolyzed by amylo-alpha-1,6-glucosidase to PA-maltooctaose (G8PA) and glucose. The ratio of the rates of 4-alpha-glucanotransferase actions on B4/85, B4/84 and B4/83 in the absence of the acceptor was 0.15, 0.42 and 1.00, respectively. The rates increased with increasing amounts of acceptor, changing the ratio of the rates to 0.09, 1.00 and 0.60 (with 0.5 mM maltohexaose) and 0.10, 1.00 and 0.58 (with 1.0 mM maltohexaose), respectively. Donor substrate specificity of GDE 4-alpha-glucanotransferase suggests complementary action of GDE and glycogen phosphorylase on glycogen degradation in the porcine liver. Glycogen phosphorylase degrades the maltooligosaccharide branches of glycogen by phosphorolysis to form maltotetraosyl branches, and phosphorolysis does not proceed further. GDE 4-alpha-glucanotransferase removes a maltotriosyl residue from the maltotetraosyl branch such that the alpha-1,6-linked glucosyl residue is retained. |
| Databáze: | OpenAIRE |
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