Details

Autor(en) / Beteiligte

• Norén, K.
• Hansen, G.H.
• Clausen, H.
• Norén, O.
• Sjöström, H.
• Vogel, L.K.

Titel

Defectively N-Glycosylated and Non-O-Glycosylated Aminopeptidase N (CD13) Is Normally Expressed at the Cell Surface and Has Full Enzymatic Activity

Ist Teil von

• Experimental cell research, 1997-02, Vol.231 (1), p.112-118

Ort / Verlag

United States: Elsevier Inc

Erscheinungsjahr

1997

Quelle

Elsevier Journal Backfiles on ScienceDirect (DFG Nationallizenzen)

Beschreibungen/Notizen

• In order to study the effects of the absence of O-glycosylation and modifications of N-glycosylation on a class II membrane protein, pig and human aminopeptidase N (CD13) were stably expressed in the ldl(D) cell line. This cell line carries a UDP-Gal/UDP-GalNAc-epimerase deficiency which blocks the conversion of glucose into galactose derivatives. Thus it is possible in the ldl(D) cell line to selectively block O-glycosylation by the omission of N-acetylgalactoseamine from the culture medium and to alter N-glycosylation by the omission of galactose. In this way selectively altered glycosylated forms of the glycoprotein aminopeptidase N can be synthesized and the effects of altered glycosylation can be studied. It is demonstrated that aminopeptidase N carries “mucin-type” O-glycans and that this is predominantly located in the stalk, which connects the catalytic headgroup to the membrane anchor. Normally glycosylated aminopeptidase N is present in the plasma membrane of the ldl(D) cells. This is also the case for the non-O-glycosylated and defectively N-glycosylated forms. This is in line with the finding that the intracellular transport APN is unaffected by the absence of O-glycosylation or by changes in N-glycosylation as the various glycosylated forms of aminopeptidase N are normally converted from the high-mannose form to the complex glycosylated form. Enzymatic activity is not influenced by the changes in glycosylation.