title: Intra- and extracellular forms of ethanol-modified O-underglycosylated galactose oxidase.
abstract: The effect of ethanol and tunicamycin on synthesis and secretion of galactose oxidase was studied in resting cells of Dactylium dendroides. Ethanol promoted an overall decrease in both intra- and extracellular enzyme levels to the same extent that it inhibited [14C]glucosamine incorporation into total protein. The carbohydrate content of the intracellular enzyme was also depressed (44%) with a simultaneous decrease in O-Ser linked oligosaccharides. The intracellular galactose oxidase obtained after exposure of mycelia to ethanol plus tunicamycin lost 86% of its carbohydrate moieties, whereas the extracellular form lost only 35%. In both cases, residual sugar moieties were not eliminated by mild alkaline treatment. These data suggest that ethanol affects O-glycosylation of galactose oxidase. O-Underglycosylation did not affect the S0.5 values for galactose but diminished the molar catalytic activity. The absence of O-Ser/Thr-linked saccharides turned the intracellular enzyme into a form more susceptible to proteolysis than that devoid of N-linked sugars (tunicamycin-treated). O-Underglycosylation had a significant effect on the renaturation-reactivation of the enzyme after denaturation with 2.4 M Gdn-HCl.
authors.affiliation: Departamento de Bioquímica, Universidade Federal do Paraná, Curitiba, PR, Brazil.
authors.forename: M H
authors.initials: MH
authors.lastname: Mendonça
authors.forename: G T
authors.initials: GT
authors.lastname: Zancan
mesh_terms: D001487:Basidiomycota / Q000201:enzymology*; D000431:Ethanol / Q000494:pharmacology*; D005692:Galactose Oxidase / Q000096:biosynthesis* / Q000235:genetics; D005944:Glucosamine / Q000378:metabolism*; D006031:Glycosylation; D007700:Kinetics; D007930:Leucine / Q000378:metabolism; D011124:Polyporaceae / Q000187:drug effects / Q000201:enzymology* / Q000254:growth & development; D011499:Protein Processing, Post-Translational / Q000187:drug effects*; D014415:Tunicamycin / Q000494:pharmacology
chemical_list: D014415:Tunicamycin; D000431:Ethanol; D005692:Galactose Oxidase; D007930:Leucine; D005944:Glucosamine