We have purified secreted acid phosphatase of Schizosaccharomyces pombe. The enzyme is N-glycosylated, the associated carbohydrate accounts for 90% of the total molecular mass and the protein moiety has a molecular mass of 54 kDa. The deglycosylated enzyme still exhibits enzymatic activity. Using antibodies recognizing the protein moiety of the enzyme we have identified two intracellular precursors of acid phosphatase: an unglycosylated membrane-bound 54-kDa form that accumulates in the presence of tunicamycin and a partially glycosylated 72-kDa form that accumulates mostly in membranes of cells grown in rich medium. We further showed that the conversion of the 54-kDa and 72-kDa forms to partially glycosylated and fully glycosylated acid phosphatase is a regulated process. Growth conditions determine how much of translated 54-kDa acid phosphatase is glycosylated to the 72-kDa form and how much remains unglycosylated in membranes. When cells are grown in a rich medium, 5% of the total acid phosphatase protein remains as unglycosylated enzyme and 8% as partially glycosylated 72-kDa form. In cells grown in the minimal medium, however, all of the 54-kDa and 72-kDa forms of acid phosphatase are rapidly processed to fully glycosylated enzyme. The 72-kDa form and the unglycosylated form of acid phosphatase are not secreted or transported to the plasma membrane.Eucaryotic secretory proteins including those of Saccharomyces cerevisiae are synthesized at the endoplasmic reticulum, are transported to the Golgi apparatus and via vesicles to the cell surface. Many of them are N-glycosylated on their secretory pathway. In yeast the pathway of Asn-linked glycosylation starts with the transfer of the oligosaccharide precursor, (GlcNAc)2(Man)9(Glc)3, from the dolichyl diphosphate to appropriate asparagine residues [l, 21. This oligosaccharide is further processed by removal of the three glucose units and a mannose unit [l, 31. Glycoproteins that are secreted have large polymannose chains added to the oligosaccharide core units, whereas glycoproteins destined to remain in the cell have the core oligosaccharide increased by 1 -4 mannose residues [4 -61.Mainly by the use of temperature-sensitive mutants that are blocked at distinct steps in the export of cell-surface glycoproteins, it has been shown that the transfer of the (Glc)3(Man)9(GlcNAc)z core oligosaccharides to the protein occurs in the endoplasmic reticulum and that extension through the addition of outer polymannose chains takes place in Golgi-like organelles [7]. Little is known concerning the regulation of the Asn-linked glycosylation pathway in yeast. Data of Chu and Malley indicate that glucose impairs Nglycosylation of invertase and that the nonglycosylated polypeptide is rapidly degraded by an endogenous protease PI.Correspondence to M. E. Schweingruber, Institut fur Allgemeine Mikrobiologie der Universitat Bern, Baltzerstrasse 4, CH-3012 Bern, SwitzerlandAbbreviations. Endoglycosidase H, endo-N-acetylglucosaminidase H ; Tris/NaCl, 20 mM Tris/HCl, 150 mM NaC1, pH ...