Enzymes involved in the synthesis of mannose-6-phosphate from glucose are normal in carbohydrate deficient glycoprotein syndrome fibroblasts.

Fibroblasts of Carbohydrate Deficient Glycoprotein Syndrome (CDGS) patients synthesize smaller lipid-linked oligosaccharides and incorporate less [3H]-mannose into glycoproteins than controls. Adding mannose, but not glucose, to the culture medium simultaneously corrects both lesions, suggesting that CDGS cells lack sufficient mannose for normal glycosylation. Since mannose for glycoprotein synthesis is assumed to come from glucose, CDGS patients could have defective enzymes in this pathway. Here we show that these enzymes are normal in five CDGS cell lines. This suggests that much of the mannose for glycoprotein synthesis in fibroblasts may come from other, as yet unidentified, pathways.