title: Australine, a pyrrolizidine alkaloid that inhibits amyloglucosidase and glycoprotein processing.
abstract: Australine [(1R,2R,3R,7S,7aR)-3-(hydroxymethyl)-1,2,7-trihydroxypyrrolizid ine] is a polyhydroxylated pyrrolizidine alkaloid that was isolated from the seeds of the Australian tree Castanospermum australe and characterized by NMR and X-ray diffraction analysis [Molyneux et al. (1988) J. Nat. Prod. (in press)]. Since swainsonine and catanospermine are polyhydroxylated indolizidine alkaloids that inhibit specific glycosidases, we tested australine against a variety of exoglycosidases to determine whether it would inhibit any of these enzymes. This alkaloid proved to be a good inhibitor of the alpha-glucosidase amyloglucosidase (50% inhibition at 5.8 microM), but it did not inhibit beta-glucosidase, alpha- or beta-mannosidase, or alpha- or beta-galactosidase. The inhibition of amyloglucosidase was of a competitive nature. Australine also inhibited the glycoprotein processing enzyme glucosidase I, but had only slight activity toward glucosidase II. When incubated with cultured cells, this alkaloid inhibited glycoprotein processing at the glucosidase I step and caused the accumulation of glycoproteins with Glc3Man7-9(GlcNAc)2-oligosaccharides.
authors.affiliation: Department of Biochemistry, University of Texas Health Science Center, San Antonio 78284-7760.
authors.forename: J E
authors.initials: JE
authors.lastname: Tropea
authors.forename: R J
authors.initials: RJ
authors.lastname: Molyneux
authors.forename: G P
authors.initials: GP
authors.lastname: Kaushal
authors.forename: Y T
authors.initials: YT
authors.lastname: Pan
authors.forename: M
authors.initials: M
authors.lastname: Mitchell
authors.forename: A D
authors.initials: AD
authors.lastname: Elbein
mesh_terms: D000470:Alkaloids; D000818:Animals; D002241:Carbohydrates / Q000096:biosynthesis; D002478:Cells, Cultured; D005087:Glucan 1,4-alpha-Glucosidase / Q000037:antagonists & inhibitors*; D005947:Glucose / Q000378:metabolism; D005959:Glucosidases / Q000037:antagonists & inhibitors; D006023:Glycoproteins / Q000378:metabolism*; D006026:Glycoside Hydrolases / Q000037:antagonists & inhibitors; D066298:In Vitro Techniques; D007212:Indolizines; D015394:Molecular Structure; D010944:Plants / Q000032:analysis; D014176:Protein Biosynthesis; D011763:Pyrrolizidine Alkaloids / Q000494:pharmacology*; D054836:Indolizidines
chemical_list: D000470:Alkaloids; D002241:Carbohydrates; D005087:Glucan 1,4-alpha-Glucosidase; D005947:Glucose; D005959:Glucosidases; D006023:Glycoproteins; D006026:Glycoside Hydrolases; D007212:Indolizines; D011763:Pyrrolizidine Alkaloids; C059794:australine; C037806:castanospermine; D054836:Indolizidines