Enzymatic synthesis of mannosyl retinyl phosphate from retinyl phosphate and guanosine diphosphate mannose.

摘要: A study was conducted to determine whether retinyl phosphate would act as substrate for the enzymatic synthesis of mannosyl phosphate. Retinyl phosphate, prepared chemically, supported growth vitamin A-deficient rats at same rate retinol. It also stimulated uptake [14C]mannose from GDP-[14C]mannose into total chloroform-methanol extractable lipid. This reaction occurred in presence ATP, Mn2+, detergent (Zonyl A), and a membrane-rich enzyme preparation livers rats, provided that lipid extract membrane alpha-L-lecithin added. Total chloroform-methanol-extractable, labeled mannolipid separated two principal mannolipids by thin-layer or column chromatography differential solvent extraction. The properties these identified them glycophospholipids: one identical with authentic synthetic dolichyl other concluded be because its incorporation radioactivity [3H]retinyl rapid hydrolysis dilute acid, formation substance cochromatographed retinol upon acid hydrolysis. ATP GTP essential stimulation synthesis, probably their protective action on substrates against phosphatases present crude fraction. pH 6.0-6.2 favored phosphate; higher (6.7-7.0)