Open AccessEffects of Gibberellic Acid and of Tunicamycin on Glycosyl‐Transferase Activities and on α‐Amylase Secretion in Barley
Author(s) -
SCHWAIGER Hubert,
TANNER Widmar
Publication year - 1979
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1979.tb04252.x
Subject(s) - tunicamycin , gibberellic acid , glycosylation , biochemistry , glycoprotein , secretion , amylase , mannose , aleurone , biology , chemistry , enzyme , botany , germination , gene , unfolded protein response
A crude membrane fraction was prepared from isolated aleurone layers, the secretory tissue of barley grains. The layers were pre‐incubated in the presence or absence of the phytohormone gibberellic acid. The membranes catalyzed the transfer of [ 14 C]mannose from GDP‐[ 14 C]mannose and of N ‐[ 14 C]acetylglucosamine from UDP‐ N ‐[ 14 C]acetylglucosamine to endogenous and exogenous dolichyl monophosphate. When gibberellic acid was present during the pretreatment the activity of the transferases was increased by a factor of two to three. A significantly increased activity was observable within four hours after the addition of gibberellic acid, whereas the gibberellic‐acid‐induced secretion of the glycoprotein α‐amylase started only after 12 h. Tunicamycin inhibited the secretion of α‐amylase by 60 to 80%. Intracellularly, however, no α‐amylase was found to accumulate. On the other hand, tunicamycin did not inhibit the rate of total protein synthesis by more than 10%. The possibility is discussed that the synthesis of the protein portion of glycoproteins is specifically inhibited, when glycosylation is prevented.