The biosynthesis of gangliosides. The incorporation of galactose, N-acetylgalactosamine and N-acetylneuraminic acid into endogenous acceptors of subcellular particles from rat brain in vitro |
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Authors: | A Arce H J Maccioni and R Caputto |
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Institution: | Departmento de Química Biológica, Instituto de Ciencias Químicas, Ciudad Universitaria, Córdoba, Argentina |
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Abstract: | Gangliosides bound to subcellular particles from rat brain were labelled by incubation of the particles (i) with CMP-N(3)H]-acetylneuraminic acid and (ii) simultaneously, with CMP-N(3)H]-acetylneuraminic acid and UDP-N-acetyl-(14)C(1)]galactosamine or with CMP-N(3)H]-acetylneuraminic acid and UDP-U-(14)C]-galactose. Analysis of the labelled gangliosides showed that in (i), (a) the labelling was mostly in the neuraminidase-labile sialyl groups, (b) rigid relationships exist between the enzymes and the sialyl acceptors; the enzymes are not free to interact with all the specific substrates present in the preparation and (c) the precursor of the trisialoganglioside was the major disialoganglioside with a sialyl 2-->8 sialyl group. In (ii), (a) precursor-product relationships between the main pools of each ganglioside apparently do not exist, (b) for the labelling of Tay-Sachs ganglioside the amount formed from hematoside was at least 2.5 times that from aminoglycolipid and (c) the major monosialoganglioside was the precursor for the major disialoganglioside with a sialyl 2-->8 sialyl group. |
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