Recent evidence for the participation of vitamin A in glycoprotein synthesis.
Recent evidence supports the concept that vitamin A plays some role in glycoprotein synthesis in a large-variety of tissues examined. Its involvement may be through participation of a retinol-linked sugar, mannosyl retinyl phosphate (MRP). Upon injection of [3H]retinol and [14C]mannose into rats, [14C, 3H]MRP could be isolated from liver and intestinal mucosa, and identified by chromatographic and hydrolytic experiments. The enzyme system that forms MRP from GDP-mannose and retinyl phosphate was located primarily in rough endoplasmic reticulum of fractionated liver cells, with some activity also in smooth membranes and Golgi apparatus. Vitamin A deficiency resulted in depressed synthesis of the rat serum glycoprotein alpha 1-macroglubin (alpha 1-MG), as shown by a decline in labeling. Analysis of the labeled alpha 1-MG from serum of normal and vitamin A-deficient rats showed this to be the result of a defect in glycosylation. The specific activity ratio (deficient:normal) of the alpha 1-MG of serum declined progressively with development of the deficiency, as a result of underglycosylation. Complete carbohydrate analysis of the alpha 1-MG of normal and deficient serum revealed a sugar loss in this glycoprotein as a result of vitamin A deficiency.
D000818:Animals; D002478:Cells, Cultured; D004721:Endoplasmic Reticulum / Q000378:metabolism; D006023:Glycoproteins / Q000096:biosynthesis*; D007413:Intestinal Mucosa; D008099:Liver; D008360:Mannosephosphates / Q000378:metabolism; D051381:Rats; D014801:Vitamin A / Q000378:metabolism / Q000502:physiology*; D014802:Vitamin A Deficiency / Q000378:metabolism; D000511:alpha-Macroglobulins / Q000378:metabolism
D006023:Glycoproteins; D008360:Mannosephosphates; D000511:alpha-Macroglobulins; D014801:Vitamin A