PubMed · 345764
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L Fridhandler, J E Berk. 1978. Macroamylasemia.. https://doi.org/10.1016/s0065-2423(08)60024-4
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Pure pancreatic juice (PPJ) from healthy human volunteers and from patients with pancreatic or liver disease was subjected to isoelectric focussing (IEF) and assayed for alpha-amylase activity. In PPJ from most normals, a single predominant form of amylase was found, comprising congruent to 83% of the total activity recovered, and having pIapp congruent to pH 6.8. In PPJ from six normals, variant principal forms of amylase were found at pH congruent to 6.4 or pH congruent to 7.3, in addition to the peak at pH 6.8. IEF patterns of PPJ from individuals with pancreatic or liver disease were indisquishable from patterns obtained with PPJ from the control group of healthy volunteers.
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 [14C]mannose from GDP-[14C]mannose and of N-[14C]acetylglucosamine from UDP-N-[14C]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 alpha-amylase started only after 12 h. Tunicamycin inhibited the secretion of alpha-amylase by 60 to 80%. Intracellularly, however, no alpha-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.