Ganglioside: Biosynthesis, Transport and location in the plasma membrane.

CAPUTTO BEATRIZ LEONOR; CAPUTTO RANWEL; DOMOWICZ MIRIAM S.; KIVATINITZ SILVIA CLARA; RAHMANN HINRICH

NATO Series H

Springer

Lugar: Berlin Heidelberg; Año: 1987; p. 251 - 258

The biosynthesis of brain gangliosides is now a process fairly well known. It is established that the ceramide moiety is synthetized in the endoplasmic reticulum while the carbohydrate moiety is synthetized in the Golgi apparatus (Landa et al., 1981). The enzyme reactions so far known in this synthesis are all single additions of one sugar in a step wise manner. The flow chart of these reactions is accepted without serious arguments even if there is a paucity of information on the enzymes and the regulation of their activities. These enzyme reactions are carried out inside vesicles where the product gangliosides are protected from the activity of outside enzymes. Apparently at a certain stage of the synthetic process the enzyme activities or the donor substrates disappear and from this stage on the pattern of gangliosides for the target organ remains unchanged. Inside the vesicles the gangliosides are conveyed by axonal transport to the nerve ending (Forman and Ledeen 1972, Landa et al., 1979) and there they are deposited in the plasma membrane by a mechanism at present poorly understood. The most popular and perhaps the most sensible current theory is that they pass from inside the vesicles to the extraplasmatic layer of the plasma membrane by a mechanism of fusion but the difficulties to accept this concept are great as you will see further on.