CARBOHYDRATE-DEFICIENT GLYCOPROTEIN SYNDROME TYPE-V - DEFICIENCY OF DOLICHYL-P-GLC-MAN(9)GLCNAC(2)-PP-DOLICHYL GLUCOSYLTRANSFERASE

Deficiency of dolichyl-P-Glc:Man(9)GlcNAc(2)-PP-dolichyl glucosyltrans ferase is the cause of an additional type of carbohydrate-deficient gl ycoprotein syndrome (CDGS type V), Clinically this type resembles the classical type Ia of CDGS caused by the deficiency of phosphomannomuta se. As a result of the glucosyltransferase deficiency in CDGS type V n onglucosylated lipid-linked oligosaccharides accumulate. The defect is leaky and glucosylated oligosaccharides are found on nascent glycopro teins. The limited availability of glucosylated lipid-linked oligosacc harides explains the incomplete usage of N-glycosylation sites in glyc oproteins. This finding is reflected in the presence of transferrin fo rms in serum that lack one or both of the two N-linked oligosaccharide s and the reduction of mannose incorporation to about one-third of con trol in glycoproteins of fibroblasts.