Retinyl phosphate mannose

In the synthesis of most glycoproteins containing mannose, the intermediate carrier of the mcmnosyl moiety is the polyene dolichol phosphate. However, in some systems, retinyl phosphate can act as the intermediate carrier between UDP-mcumose tmd the acceptor glycoprotein. Retinyl phosphate mannose seems to be involved especially in the synthesis of hydrophobic regions of glycoproteins (DeLuca, 1977 Frot-Coutaz et al., 1985). 

Biosynthesis of Retinyl Phosphate and Retinyl Phosphate Mannose... 

Rosso, G., DeLuca, L., Warren, C.D. Wolf, G. (1975) Enzymatic Synthesis of Mannosyl Retinyl Phosphate from Retinyl Phosphate and Guanosine Diphosphate Mannose , Journal of Lipid Research, 16, 235-43... 

Rosso, G.C., Masushige, S., Quill, H. Wolf, G. (1977) Transfer of Mannose from Mannosyl Retinyl Phosphate to Protein , Proceedings of the National Academy of Sciences, USA, 74, 3762-6... 

In summary, retinyl mannosyl phosphate has the P-anomeric configuration, like the dolichyl mannosyl phosphate, since it yielded mannose-2-phosphate upon mild alkaline cleavage (Rosso et al, 1976). Its properties... 

A possible transfer of mannose from retinyl mannosyl phosphate to polypeptide was first indicated by the studies of Maestri and De Luca (1973), though these did not prove that retinyl mannosyl phosphate was the mannosyl donor. In a more detailed analysis Rosso etaL (1977) used a radioactive label largely free of dolichyl mannosyl phosphate in a cell-free system and obtained a clear-cut incorporation of mannose from retinyl mannosyl phosphate into a substance with the solubility properties of protein and which was labile to proteolysis. Some free mannose, its 1-phosphate and retinyl mannosyl phosphate were also present at the end of the incubation, but no large mannolipid was detected. Dolichy CJmannosyl phosphate did not give any transfer of [ C] mannose to protein and further support for a distinctive retinol pathway came from the effects of EDTA. This totally failed to block transfer from retinyl [ mannosyl phosphate, under conditions where block... 

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