Sialoglycoproteins biosynthesis

The biosynthesis of gangliosides and sialoglycoproteins in retina has been studied in vitro" measuring the incorporation of H-NeuNAc from CMP- H-NeuNAc into endogenous acceptors of bovine retina. 

NeuAc and its activation to CMP-NeuAc, which is the nucleotide substrate for all sialic acids. After transport to the Golgi apparatus, CMP-NeuAc is then transferred to various oligosaccharide chains of gangUosides or sialoglycoproteins. NeuAc can also be degraded by NeuAc pyruvate lyase into ManNAc. Note that all the enzymes required for completion of the sialic acid biosynthesis are found in the cytosol, except for CMP-NeuAc synthetase, which is found in the nucleus. GL, glycoUpid GP, glycoprotein. 

Incorporation studies with radioactive glucosamine, galactosamine and mannosamine confirmed the biosynthesis of sialoglycoproteins in avian tissues (Channon et al. 1972, Scott and Anastassiadis 1978). 

Jokinen, M., Andersson, L. C., and Gahmberg, C. G., 1985, Biosynthesis of the major human red blood cell sialoglycoprotein, glycophorin A, J. Biol. Chem. 260 11314-11321. 

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