1-Deoxymannojirimycin inhibits Golgi-mediated processing of glycoprotein in Xenopus oocytes.

We prepared in vitro an mRNA transcript coding for the erythroagglutinating subunit of the kidney bean glycoprotein phytohemagglutinin, E-PHA. The mRNA, injected into Xenopus oocytes, synthesized E-PHA carrying two Asn-linked carbohydrate chains, one of which was processed and acquired resistance to endo-beta-N-acetylglucosaminidase H, as occurs in the native bean cells. When the mannose analog 1-deoxymannojirimycin, an inhibitor of mammalian Golgi mannosidase I, was included in the oocyte culture medium, the acquisition of endo-beta-N-acetylglucosaminidase H resistance was abolished, indicating that also in an amphibian cell the inhibitor blocks a key reaction in Golgi-mediated processing.